title: Presidency of Joe Biden

text: On January 20, 2021, the Biden administration issued a moratorium on deportations from the U.S. Department of Homeland Security (DHS) for the first 100 days of his presidency. On January 22, Texas Attorney General Ken Paxton sued the Biden administration for violating Biden's written pledge to cooperatively work with the state of Texas. A federal judge in Texas subsequently issued a temporary restraining order barring the Biden administration from enforcing its moratorium, citing the lack of "any concrete, reasonable justification for a 100-day pause on deportations."


title: Presidency of Joe Biden

text: On January 21, 2021, Biden proposed a bill that, if passed, would replace the word "alien" with "noncitizen" in U.S. immigration law. The following day, Biden had a call with Mexican president Andrés Manuel López Obrador. On the call, Biden and López Obrador spoke about immigration, where Biden spoke of reducing immigration from Mexico to the U.S. by targeting what Biden deemed as root causes. According to an Associated Press report, López Obrador noted that Biden pledged $4 billion to "help development in Honduras, El Salvador and Guatemala — nations whose hardships have spawned tides of migration through Mexico toward the United States."


title: Presidency of Joe Biden

text: On January 23, Biden proposed an immigration bill aiming to give a path to citizenship to eleven million immigrants living in the U.S. without a permanent legal status. The bill would also make it easier for certain foreign workers to stay in the U.S. Senate Majority Whip Dick Durbin called the bill "aspirational". It is widely expected not to pass both houses of Congress without significant revision.


title: Presidency of Joe Biden

text: Biden instructed the U.S. Immigration and Customs Enforcement (ICE) to focus on violent offenders of immigration laws rather than all offenders of immigration laws.


title: Presidency of Joe Biden

text: In February 2021, it was reported that DHS agents who had been empowered by Trump to enact his anti-immigration policies were resisting and defying Biden's immigration policies. The union representing ICE agents signaled that its agents would not accept reversals of Trump policies.


title: Presidency of Joe Biden

text: In March 2021, the Biden administration granted temporary protected status to Venezuelans fleeing the country amidst the ongoing political and economic crisis.


title: Presidency of Joe Biden

text: On June 1, 2021, the DHS officially terminated the Trump-era "Remain in Mexico" policy, which mandated that all asylum seekers from Central America were to wait in Mexico pending their court cases; however, a health order from March 2020 allowed the border authorities to send migrants back for the duration of the COVID-19 pandemic have remained in place. However, on August 14, 2021, a federal judge in Texas ordered the Biden administration to reimplement the policy; the Supreme Court placed a pause on the ruling to give the administration time for arguments. On August 24, 2021, the Supreme Court ruled that the Biden administration must comply with the lower court's ruling to reinstate the policy.


title: Presidency of Joe Biden

text: Early on in Biden's tenure, a surge in unaccompanied minors at the U.S. border stirred controversy. According to a 2021 "Politico" report, Republicans expected prior to Biden taking office that there would be a border surge at the start of 2021 (due to seasonal patterns and regional crises) and coordinated to make it a central issue in the lead-up to the 2022 mid-term elections. The number of migrants arriving in the U.S. from Central America had been rising since April 2020 due to ongoing violence, natural disasters, food insecurity, and poverty in the region. In February 2021, the U.S. Border Patrol reported a 61% increase in encounters with unaccompanied children from the month before. The reported 5,858 encounters in January to 9,457 in February constituted the largest one-month percentage increase in encounters with unaccompanied children since U.S. Customs and Border Protection began recording data in 2010. By the end of April 2021, the number of children held in Border Patrol facilities fell by 84%, placing them under HHS care.


title: Presidency of Joe Biden

text: On March 24, 2021, Biden tasked Vice President Harris to reduce the number of unaccompanied minors and adult asylum seekers. She is also tasked with leading the negotiations with Mexico, Honduras, Guatemala, and El Salvador.


title: Presidency of Joe Biden

text: The number of migrant families and unaccompanied children entering the U.S. from across the Southwest border steeply declined in August, September, and October 2021.


title: Presidency of Joe Biden

text: As a practicing Catholic, Biden has taken a public position of dissent against the Catholic position opposing free-choice in the abortion issue. Biden's position of dissent has raised the question of whether his public office might allow him to influence the outcomes of debates currently taking place with the Catholic Church concerning the abortion issues. Although the Vatican has taken a mediating position concerning Biden's dissent concerning the free-choice issue by allowing him to take Communion in Rome while visiting the Pope, other local churches such as a local parish in South Carolina have in the past blocked Biden from taking Communion as a public declaration of the Church's position against abortion in an attempt to discourage other parishioners from taking a similar position of dissent against Church policy.


title: Presidency of Joe Biden

text: During his early days in office, Biden focused on "advancing equity, civil rights, racial justice and equal opportunity." According to "The New York Times", Biden's early actions in office focused on racial equality more than any president since Lyndon B. Johnson, who passed the Civil Rights Act of 1964. On January 25, 2021, Biden signed an executive order that lifted the ban on transgender military service members. This reversed a memorandum imposed by Trump.


title: Presidency of Joe Biden

text: The Biden administration is seeking to put Harriet Tubman on the twenty-dollar bill. This effort follows that of the Obama administration, which was blocked by Steven Mnuchin. Press secretary Psaki said it was important that U.S. money and notes reflect the "history and diversity" of the country and that putting Tubman on the twenty-dollar bill would do so.


title: Presidency of Joe Biden

text: On January 20, 2021, the Biden administration issued an Executive Order entitled Advancing Racial Equity and Support for Underserved Communities Through the Federal Government increasing the federal government's anti-bias enforcement against government contractors. The intent is heightened investigations and audits by the Department of Justice as well as more detailed follow-up inquiries with government contractors, with an emphasis on combatting pay discrimination. Also in January, Biden directed the U.S. Department of Justice to reduce their usage of private prisons and ordered the attorney general to not renew contracts with private prisons, citing the need to "reduce profit-based incentives" for the incarceration of racial minorities.


title: Presidency of Joe Biden

text: Three days after the Atlanta spa shootings that killed 8 people, including 6 Asian women, Biden and Vice President Harris travelled to Atlanta. They spoke to Asian American and Pacific Islander advocates and leaders and condemned sexism, and racism against Asian Americans.


title: Presidency of Joe Biden

text: Biden made Juneteenth (June 19) a federal holiday in 2021, celebrating the end of slavery in the U.S.


title: Presidency of Joe Biden

text: In October 2022, Biden pardoned all past federal marijuana possession charges and announced an inquiry into whether cannabis should be removed from Schedule I of the Controlled Substances Act.


title: Presidency of Joe Biden

text: In December 2021, the Biden administration ended a long-standing restriction on sales of abortion pills through the mail. This decision came amidst legal cases and Supreme Court decisions that jeopardized abortion access in the United States.


title: Presidency of Joe Biden

text: Following the U.S. Supreme Court overturning "Roe v. Wade" and "Planned Parenthood v. Casey" on June 24, 2022, in "Dobbs v. Jackson Women's Health Organization," Biden addressed the nation in the Cross Hall of the White House. He mentioned that "it’s a sad day ... for the country" and "with Roe gone, ... The health and life of women in this nation are now at risk." In addition, he attacked the Court saying "With this decision, the conservative majority of the Supreme Court shows how extreme it is" and "They have made the United States an outlier among developed nations in the world." Regarding action, Biden stated that his administration will defend the right of women to seek an abortion in another state where abortion is legal and help protect a woman's access to contraception and abortion pills approved by the FDA. He also called on Congress to codify "Roe v. Wade", saying "No executive action ... can do that.". But stated that if Congress did not have the votes to codify, that the voters would have to take action by "elect[ing] more senators and representatives who will codify a woman’s right to choose into federal law."


title: Presidency of Joe Biden

text: During a press conference at the 2022 Madrid NATO Summit, Biden expressed support for providing an exception to the filibuster to codify "Roe v. Wade."


title: Presidency of Joe Biden

text: The Biden administration rescinded a Trump administration policy that curtailed the use of consent decrees that had been used by previous administrations in their investigations of misconduct in police departments.


title: Presidency of Joe Biden

text: Biden proposed in his fiscal 2022 budget to more than double funding for the Community Oriented Policing Services (COPS) Hiring Program, which helps state and local governments to hire law enforcement officers.


title: Presidency of Joe Biden

text: In a national address in March 2021, following mass shootings in the Atlanta area and Boulder, Colorado, Biden advocated for further gun regulations, such as a restored ban on assault weapons and a high-capacity magazine ban, as well as reinforcing preexisting background checks.


title: Presidency of Joe Biden

text: Following the Robb Elementary School shooting on May 24, 2022, President Biden addressed the nation. The following week, he again called on Congress to pass an assault weapons and high-capacity magazine ban, as well as red flag laws and other legislation. The Bipartisan Safer Communities Act was eventually passed into law as a result of this.


title: Presidency of Joe Biden

text: The Biden administration reversed the Trump administration's method of using the National Space Council to coordinate commercial, civil, and military space policies, instead using the National Security Council to issue national security memoranda instead of the Space Council's space policy directives. The Biden administration renewed the National Space Council, chaired by Vice President Harris, "to assist the president in generating national space policies, strategies, and synchronizing America's space activities." Harris held meetings with the leaders of five countries to discuss international cooperation on space issues.


title: Presidency of Joe Biden

text: The Biden administration continued the Artemis program to send people back to the Moon. The administration also emphasized the role of NASA in studying climate change.


title: Presidency of Joe Biden

text: Biden appointed Bill Nelson, an astronaut and former U.S. Senator, to the post of NASA administrator. Nelson was confirmed unanimously by the Senate in April 2021.


title: Presidency of Joe Biden

text: In April 2021, as part of his first annual budget request, Biden proposed a $24.8 billion budget for NASA in 2022, a $1.5 billion increase on what Congress allocated to 2021. The proposal includes funding for the Artemis program for a new crewed Moon landing mission. The proposal also included a 12.5% increase for NASA's Earth Science Division, as well as a 22% increase for the National Oceanic and Atmospheric Administration, which operates a fleet of weather satellites; both measures aimed to use space tools to study and mitigate climate change.


title: Presidency of Joe Biden

text: In August 2022, Biden announced that the Department of Education would cancel certain federally owned student debt. Borrowers earning under $125,000 per year, or under $250,000 for married couples who file jointly, would be eligible for up to $10,000 in loan forgiveness. Borrowers who received a Pell Grant while attending college could qualify for up to an additional $10,000 in loan forgiveness, for a total of $20,000. The administration estimated that about 43 million borrowers would be covered by the plan, including about 20 million individuals whose student debt would be completely forgiven. On August 9th, 2022, Biden signed the CHIPS and Science Act, which supports STEM education with funding.


title: Presidency of Joe Biden

text: On January 22, 2021, Biden signed his first bill, H.R. 335 into law, providing a waiver to the law preventing appointment of a Secretary of Defense who had been on active duty in the armed forces within the past seven years; this was the third time such a waiver was granted by Congress. Retired army four-star general Lloyd Austin was confirmed by the Senate in a 93–2 vote that same day, making Austin the first African-American Defense Secretary.


title: Presidency of Joe Biden

text: Austin has said his number one priority is to assist COVID-19 relief efforts, pledging he would "quickly review the Department's contributions to COVID-19 relief efforts, ensuring that we're doing everything that we can to help distribute vaccines across the country and to vaccinate our troops and preserve readiness."


title: Presidency of Joe Biden

text: On February 10, 2021, Biden visited the Pentagon for the first time as U.S. president. In remarks to service members alongside Vice President Kamala Harris and Defense Secretary Lloyd Austin, Biden announced a U.S. Department of Defense-led China task force "to provide a baseline assessment of department policies, programs and processes in regard to the challenge China poses."


title: Presidency of Joe Biden

text: On June 18, 2021, the administration removed eight MIM-104 Patriot anti-missile batteries from Saudi Arabia, Jordan, Kuwait, and Iraq, removed the THAAD anti-missile defense system from Saudi Arabia, and announced that most jet squadrons and hundreds of American troops would be withdrawn from the region. The changes come in light of both de-escalating tensions with Iran and the administration changing its focus on countering China.


title: Presidency of Joe Biden

text: After taking office, Biden heavily restricted the use of armed drones and drone strikes. After Biden's first year in office, drone strikes had hit a 20-year low and were heavily limited by the administration.


title: Presidency of Joe Biden

text: Biden has said the U.S. needs to "get tough" on China and build "a united front of U.S. allies and partners to confront China's abusive behaviors and human rights violations." He described China as the "most serious competitor" that poses challenges on the "prosperity, security, and democratic values" of the U.S.


title: Presidency of Joe Biden

text: Biden nominated Antony Blinken to serve as Secretary of State who took office on January 26, 2021. During his nomination hearing, Blinken said that previous optimistic approaches to China were flawed, and that Biden's predecessor, Donald Trump, "was right in taking a tougher approach to China" but he "disagree[s] very much with the way [Trump] went about it in a number of areas." He endorsed former Secretary of State Mike Pompeo's report that China is committing a genocide against Uyghur Muslims.


title: Presidency of Joe Biden

text: In March 2021, Secretary of State Antony Blinken, National Security Advisor Jake Sullivan and other administration officials met with the Chinese Communist Party Politburo member Yang Jiechi, Chinese foreign minister Wang Yi, and other Chinese officials in Alaska with heated exchanges on China's human rights abuses, cyberattacks, its threats against Taiwan, its crackdown in Xinjiang and Hong Kong, and other issues of U.S. interest. The Chinese side countered: "The U.S. does not have the qualification to speak to China from a position of strength [and] does not serve as a model to others [and] China's development and strengthening is unstoppable."


title: Presidency of Joe Biden

text: "The Washington Post" reported that the Biden administration got "a taste of China's 'wolf warrior' diplomacy" during the first meeting with its Chinese counterpart, which was "remarkably undiplomatic", adding "China's diplomats appeared more forceful than they had been in any public meeting during President Trump's term." "The Atlantic" published an article saying that the Biden team "flushed Beijing's true intentions out into the open for the world to see", quoting a senior administration official's comment that it is "increasingly difficult to argue that we don't know what China wants."


title: Presidency of Joe Biden

text: In April 2021, it was reported that the Biden administration was rallying U.S. allies in consideration of a boycott of the 2022 Winter Olympics in Beijing. The U.S. Department of State spokesman Ned Price told reporters that a joint boycott "is something that we certainly wish to discuss."


title: Presidency of Joe Biden

text: In May 2021, the administration removed Chinese mobile manufacturer Xiaomi from the Chinese military blacklist, reversing the previous administration's decision.


title: Presidency of Joe Biden

text: On June 3, 2021, Biden announced an executive order that would come into effect from August 2, and ban Americans from investing into 59 Chinese firms, including Huawei. Before it was announced, China said it would retaliate against it.


title: Presidency of Joe Biden

text: In October 2021, Biden said he is concerned about Chinese hypersonic missiles, days after China tested a nuclear-capable hypersonic missile that circled the globe before speeding towards its target.


title: Presidency of Joe Biden

text: In December 2021, a coalition of Jewish organizations, including the American Jewish Committee and the Rabbinical Assembly, issued an open letter to Biden urging additional action in response to the Uyghur genocide.


title: Presidency of Joe Biden

text: On 18 September 2022, it was reported by Reuters that "Joe Biden said U.S forces would defend Taiwan in the event of a Chinese invasion, his most explicit statement on the issue, drawing an angry response from China that said it sent the wrong signal to those seeking an independent Taiwan." The policy was stated in contrast to Biden's previous exclusion of boots-on-the-ground and planes-in-the-air for U.S. support for Ukraine in its current conflict with Russia.


title: Presidency of Joe Biden

text: In February 2020, the Trump administration made a deal with the Taliban to completely withdraw U.S. forces by May 1, 2021. In April 2021, President Biden formally announced that American troops would instead withdraw from Afghanistan by September 11, 2021, which would signal an end to the U.S.'s longest war. According to Princeton professor Julian E. Zelizer, Biden "clearly learned a great deal from his time in the Obama presidency", and demonstrated that "he is a politician capable of learning and evolving, contrary to some of the skeptics in the primaries who thought he didn't understand how politics had changed." According to "Washington Post" journalist Steven Levingston, "Obama listened to military leaders who advised him that withdrawal would be a mistake. Biden, meanwhile, was the top administration official arguing for a much more limited role for American forces in Afghanistan. Later, Biden would go on to say that he could tell by Obama's 'body language' that he agreed with that assessment — even though he ultimately rejected it."


title: Presidency of Joe Biden

text: Soon after the withdrawal of U.S. troops started, the Taliban launched an offensive against the Afghan government, quickly advancing in front of a collapsing Afghan Armed Forces. President Biden defended the withdrawal, saying "I trust the capacity of the Afghan military, who is better trained, better equipped and ... more competent in terms of conducting war."


title: Presidency of Joe Biden

text: By early July 2021, most of the American troops in Afghanistan were withdrawn. Biden addressed the withdrawal, stating that: "The likelihood there’s going to be the Taliban overrunning everything and owning the whole country is highly unlikely." On August 15, amid an offensive by the Taliban, the Afghan government collapsed, Afghan President Ashraf Ghani fled the country and Kabul fell to the Taliban. Biden reacted by ordering 6,000 American troops to assist in the evacuation of American personnel and Afghan allies. He has been criticized over the manner of the American withdrawal.


title: Presidency of Joe Biden

text: On August 16, Biden addressed the "messy" situation, taking responsibility for it ("the buck stops with me"), and admitting that the situation "unfolded more quickly than we had anticipated". He defended his decision to withdraw, saying that Americans should not be "dying in a war that Afghan forces are not willing to fight for themselves", since the "Afghan military collapsed [against the Taliban], sometimes without trying to fight". Biden partly attributed the lack of early evacuation of Afghan civilians to the Afghan government's opposition of a "mass exodus" which they thought would cause a "crisis of confidence".


title: Presidency of Joe Biden

text: On 26 August, a suicide attack was carried out by the Islamic State of Iraq and the Levant - Khorasan Province at the Hamid Karzai International Airport, killing more than 170 people, including at least 62 Afghan civilians, 13 US service members, two British nationals and the child of a third British national. Biden made a public address following the attack, in which he honoured the American service members who were killed, calling them "heroes" and saying they lost their lives "in the service of liberty", and stated that the US had evacuated more than 100,000 Americans, Afghans, and others. He expressed deep sorrow for the Afghan victims as well. Biden said to those who wished harm upon the US that "we will hunt you down and make you pay." Biden received increasingly harsh criticism from both Republicans and Democrats in the US Congress, with Republicans calling for his resignation or for his impeachment.


title: Presidency of Joe Biden

text: After the Taliban takeover of Afghanistan, the Biden administration froze about $9 billion in assets belonging to the Afghan central bank, blocking the Taliban from accessing these billions of dollars in reserves held in U.S. bank accounts.


title: Presidency of Joe Biden

text: In February 2022, Biden signed an executive order that seeks to unfreeze approximately $3.5 billion of Afghan assets in the U.S. for the purpose of humanitarian assistance in Afghanistan.


title: Presidency of Joe Biden

text: On July 31, 2022, Al-Qaida leader Ayman al-Zawahiri was killed in Kabul by an American drone strike approved by Biden.


title: Presidency of Joe Biden

text: Biden hosted a three-day U.S.-Africa summit in Washington in December 2022, attended by 49 African national leaders. The meeting was the first such summit since 2014. The leaders of every African nation in good standing with the African Union (AU), except Eritrea) were invited to the summit. The leaders of African nations not in good standing with the AU (mostly those who had come to power through military coups) were also not invited.


title: Presidency of Joe Biden

text: At the summit, Biden announced U.S. support for the AU joining the G20 group of major economies, a long-sought goal for Africa. The summit was part of a broader effort by the U.S. to rebuilt U.S.-African relations and counter Chinese influence on the continent. During the summit, the administration announced $800 million in new deals with Cisco Systems and Cybastion to combat cyberthreats targeting Africa, a bid to blunt the dominance of the Chinese firm Huawei in Africa. The administration also signed a memorandum of understanding in support of the African Continental Free Trade Area to reduce trade barriers in Africa, and committed $55 billion to Africa over the next three years, focused on preexisting U.S. initiatives, such as the trade-focused Prosper Africa and Africa Growth and Opportunity Act, as well as the Power Africa initiative, which aims to increase connections of Africans to the electric grid). The administration also emphasized initiatives in technology and cybersecurity, health, clean energy and the environment, and other areas. Biden committed an additional $2 billion for emergency humanitarian aid and $11 billion for food security programs in Africa. The administration also expanded ties with West Africa, including support for infrastructure improvements at the Benin seaport of Cotonou, a key part of the West African economy. Biden appointed longtime U.S. diplomat Johnnie Carson to coordinate implementation of U.S. actions following up from the summit.


title: Presidency of Joe Biden

text: During the 2022 summit, Biden and senior administration officials also met privately with six African leaders facing elections in 2023, pushing them to ensure free and fair elections in their nations.


title: Presidency of Joe Biden

text: Senator Bob Menendez, the Democratic chairman of the Senate Foreign Relations Committee, has criticized the Biden administration for hesitating to impose sanctions on the governments of Sudan and Ethiopia, where many atrocities and war crimes were committed in the Tigray War.


title: Presidency of Joe Biden

text: On April 24, 2021, the Biden administration declared that the Turkish killings of Armenians at the start of the 20th century were a genocide. He is the first U.S. president to ever officially recognize the Armenian genocide.


title: Presidency of Joe Biden

text: In July 2022, President Biden signed an executive order aimed at deterring the wrongful detention of Americans abroad. According to an estimate by The James W. Foley Legacy Foundation, there are at least 67 U.S. citizens who are currently imprisoned abroad. The foundation further estimates that 90% of those are wrongly detained by foreign governments hostile to the U.S., including Venezuela, Russia, China, Iran, and others. Dozens of families of Americans who are detained abroad say President Biden has failed to adequately address the crisis. They formed a group called "Bring Our Families Home Campaign" to pressure Biden to do more.


title: Presidency of Joe Biden

text: In March 2021, Biden held a virtual meeting with leaders of Japan, India and Australia, an alliance of countries known as the Quadrilateral Security Dialogue, or the Quad, that work together to address China's expansionism in the Indo-Pacific region. A few days later, the administration officials, including secretary of state Antony Blinken and secretary of defense Lloyd Austin, met with U.S. allies in Asia and imposed sanctions on senior Chinese officials. Austin also visited India to deepen the defense ties between the two countries. In September 2021, Biden hosted the first in-person meeting of Quad at the White House.


title: Presidency of Joe Biden

text: On May 23, 2022, Biden launched the Indo-Pacific Economic Framework for Prosperity (IPEF) to counter growing Chinese economic and political influence in the Indo-Pacific region. At the time of its launch, the IPEF had 12 partners including Australia, Brunei, India, Indonesia, Japan, South Korea, Malaysia, New Zealand, the Philippines, Singapore, Thailand, and Vietnam. In response, China described the proposed grouping as a "closed and exclusive club." National Security Adviser Jake Sullivan defended the IPEF by highlighting the diverse nature of the grouping's membership.


title: Presidency of Joe Biden

text: In August 2022, the Biden administration announced that it will be hosting the White House-Pacific Island summit in September 2022 which will coincide with the week of the 77th session of the United Nations General Assembly.


title: Presidency of Joe Biden

text: On the day of Biden's inauguration, the Russian government urged the new U.S. administration to take a "more constructive" approach in talks over the extension of the 2010 New START treaty, the sole remaining agreement limiting the number of U.S. and Russian long-range nuclear warheads. In Biden's first telephone call as president with Russian President Vladimir Putin, on January 26, 2021, Biden and Putin agreed to extend the New START treaty (which was set to expire in February 2021) by an additional five years.


title: Presidency of Joe Biden

text: Biden and his administration condemned human rights violations by the Russian authorities, calling for the release of detained dissident and anti-corruption activist Alexei Navalny, his wife, and the thousands of Russians who had demonstrated in his support; the U.S. called for the unconditional release of Navalny and the protestors and a credible investigation into Navalny's poisoning. On March 2, 2021, the U.S. and European Union imposed coordinated additional sanctions on Russian officials, as well as the FSB and GRU, over Navalny's poisoning and imprisonment. The State Department also expanded existing sanctions from the Chemical and Biological Weapons Control and Warfare Elimination Act that had been imposed after the poisoning of Skripal. The Biden administration is also planning to impose sanctions against Russia because of the 2020 SolarWinds cyberespionage campaign, which compromised the computer systems of nine federal agencies. Biden's national security adviser Jake Sullivan said the response "will include a mix of tools seen and unseen, and it will not simply be sanctions."


title: Presidency of Joe Biden

text: The Biden administration's comprehensive review into Russian activities has included an examination of reports that the Russian government offered bounties to kill U.S. troops in Afghanistan. The Biden administration said intelligence community has only "low to moderate" confidence in reports due to the fact that the bounty reports originated from "detainee reporting and because of the difficult operating environment in Afghanistan." Biden called Russian President Vladimir Putin a "killer" in an ABC News interview, and said that Russia would pay a price for election meddling.


title: Presidency of Joe Biden

text: On May 19, 2021, the Biden administration lifted CAATSA sanctions on the Nord Stream 2 pipeline project between Russia and Germany. Despite Biden's personal opposition to the project, the U.S. State Department says that it concluded that it was in the "U.S. national interest" to waive the sanctions. Russian Deputy Foreign Minister Sergei Ryabkov welcomed the move as "a chance for a gradual transition toward the normalisation of our bilateral ties."


title: Presidency of Joe Biden

text: On June 16, 2021, Biden met with Putin in Geneva, Switzerland. The two presidents discussed a number of topics, including stable policy on climate change, nuclear proliferation, and cybersecurity. Russia's activities regarding Ukraine, Alexei Navalny, Belarus, and nationals jailed in each other's countries. The summit was significantly shorter than expected, only lasting three and a half of the predicted five hours. Putin praised Biden as a knowledgeable and shrewd negotiator the next day.


title: Presidency of Joe Biden

text: In November 2021, Putin stated that an expansion of NATO's presence in Ukraine, especially the deployment of any long-range missiles capable of striking Russian cities or missile defense systems similar to those in Romania and Poland, would be a "red line" issue for Russia. In December 2021, Putin asked President Joe Biden for legal guarantees that NATO wouldn't expand eastward or put "weapons systems that threaten us in close vicinity to Russian territory." The U.S. and NATO have rejected Putin's demands.


title: Presidency of Joe Biden

text: On February 24, 2022, Biden condemned Russia's invasion of Ukraine, saying Putin "chose this war" and calling him "the aggressor". He announced new sanctions against Russia. On February 25, the White House announced the US would personally sanction Putin and foreign minister Sergey Lavrov. On February 28, the Biden administration announced sanctions against Russia's central bank, prohibiting Americans from doing business with the bank and freezing the bank's assets. On March 29, 2022, Biden appeared to heighten his condemnation concerning Putin made at the end of his NATO trip to Europe, stating that he makes "no apologies" for previously stating that "Putin cannot remain in power". On April 12, he called the war a "genocide". Biden criticized the Kremlin for "idle comments" on the possible use of nuclear weapons.


title: Presidency of Joe Biden

text: On April 28, Biden asked Congress for an additional $33 billion to assist Ukraine, including $20 billion to provide weapons to Ukraine. On May 10, the House passed legislation that would provide $40 billion in new aid to Ukraine. The "New York Times" reported that the United States provided real-time battlefield targeting intelligence to Ukraine that helped Ukrainian forces kill Russian generals and sink the Russian warship "Moskva". The Biden administration has pledged to help the International Criminal Court (ICC) to prosecute Putin and others for war crimes committed during the invasion of Ukraine.


title: Presidency of Joe Biden

text: The 2022 Russian invasion of Ukraine instigated significant and substantial support to Ukraine during the Biden presidency including two dozen military aid packages to assist them against the invasion. On 28 October 2022 the Pentagon announced the 24th Presidential drawdown of materiel worth $275 million; the security assistance has totalled $18.5 billion to Ukraine since January 2021. The aid includes 500 Excalibur precision-guided 155mm artillery rounds, 2000 155mm remote anti-armor mine systems, more than 1,300 anti-armor weapons, more than 2.75 million rounds of small arms ammunition, more HIMARS rockets, 125 Humvees, and four satellite communications antennas for Ukraine's command and control systems, as well as training for operation of the NASAMS units. Two NASAMS units arrived in Ukraine on 7 November 2022.


title: Presidency of Joe Biden

text: President Biden promised to repair "strained" relationships with European allies in contrast to his predecessor Trump. "An attack on one is an attack on all. That is our unshakeable vow," Biden said, referring to Article 5 of the North Atlantic Treaty (the mutual defense clause). Biden pledged support for the European project and for Ukraine's sovereignty as well as the need for global cooperation on fighting the pandemic and climate change.


title: Presidency of Joe Biden

text: U.S. relations with France deteriorated in September 2021 due to fallout from the AUKUS security pact between the United States, the United Kingdom, and Australia, which aimed to counter Chinese power in the Indo-Pacific region. As part of the agreement, the U.S. agreed to provide nuclear-powered submarines to Australia. After entering into the agreement, the Australian government canceled an agreement that it had made with France for the provision of French conventionally powered submarines. The deal angered the French government, which recalled its ambassador to the U.S. (Philippe Étienne) as well as the ambassador to Australia. Amid the diplomatic row, the French Foreign Ministry contended that it had been subjected to "duplicity, disdain and lies" and French foreign minister Jean-Yves Le Drian called the deal a "stab in the back". In a conciliatory call a few days later, Biden and French President Emmanuel Macron agreed to reduce bilateral tensions, and the White House acknowledged the crisis could have been averted if there had been open consultations between allies. A month later, Biden met Macron, telling him his administration was "clumsy" and that he was "under the impression that France had been informed long before" that France's deal with Australia was "not going through".


title: Presidency of Joe Biden

text: In February 2022, amid rising tensions between Ukraine and Russia, the Biden administration faced questions for its year-long failure to nominate an ambassador to Ukraine.


title: Presidency of Joe Biden

text: The Biden administration has expressed interest in re-engaging with Iran on the Iran nuclear deal. Biden's predecessor, President Trump,


title: Presidency of Joe Biden

text: withdrew from the deal in 2018, resulting in swift backlash from international community. Secretary of State Antony Blinken said the U.S. would be interested in re-entering the agreement so long as Iran shows "strict compliance". Blinken did not rule out a military intervention to stop Iran from obtaining nuclear weapons.


title: Presidency of Joe Biden

text: On February 25, 2021, President Biden ordered retaliatory airstrikes on buildings in Syria that the Department of Defense said were used by Iranian-backed militias to carry out rocket attacks on U.S. targets in Iraq. The operation was the first known use of military force by the Biden administration. The attacks prompted condemnation from many Democratic members of Congress. Senator Tim Kaine of Virginia questioned the administration's "legal justification for acting without coming to Congress." Representative Ro Khanna (D-CA) claimed that "the Administration should have sought Congressional authorization."


title: Presidency of Joe Biden

text: In July 2022, Biden met with Israeli Prime Minister Yair Lapid to discuss the Iran nuclear deal and said that he continued to favor diplomacy. Lapid, however, expressed that only military threat would deter Iran from pursuing a nuclear program.


title: Presidency of Joe Biden

text: On February 1, 2021, Biden condemned the Myanmar coup d'état and called for the release of detained officials. Biden also left open the door to re-imposing sanctions on the country, saying in a statement that "[t]he United States removed sanctions on Burma over the past decade based on progress toward democracy. The reversal of that progress will necessitate an immediate review of our sanction laws and authorities, followed by appropriate action."


title: Presidency of Joe Biden

text: On March 5, 2021, Biden imposed sanctions on Myanmar's Ministry of Home Affairs and Ministry of Defence and certain junta conglomerates. On March 22, 2021, Secretary of State Antony Blinken announced sanctions on several military generals in response to a violent crackdown on peaceful protests.


title: Presidency of Joe Biden

text: Biden has reiterated his commitment to maintaining peace in Northern Ireland by resisting the possibility of a hard border as a result of Brexit. When asked by "The Irish Times" in March 2021 about comments made by Irish foreign minister Simon Coveney that the UK "cannot be trusted" on the Northern Ireland protocol, White House press secretary Jen Psaki said that "President Biden has been unequivocal about his support for the Good Friday Agreement." As part of his own Irish-American heritage, Psaki said that Biden "has a special place in his heart for the Irish", underpinning his commitment to Northern Ireland's peace.


title: Presidency of Joe Biden

text: Biden ordered a halt in the arms sales to Saudi Arabia and the United Arab Emirates which the Trump administration had previously agreed to. Two years after Jamal Khashoggi's assassination, Avril Haines, the Director of National Intelligence under Biden's administration, announced that the intelligence report into the case against the Saudi government would be declassified. It was reported that Crown Prince Mohammed bin Salman would be blamed for the murder, as was concluded by the CIA.


title: Presidency of Joe Biden

text: On February 4, 2021, the Biden administration announced that the U.S. was ending its support for the Saudi-led bombing campaign in Yemen. President Biden in his first visit to the State Department as president said "this war has to end" and that the conflict has created "a humanitarian and strategic catastrophe." However, the details of the end of American involvement in the war have yet to be released as of April 2021.


title: Presidency of Joe Biden

text: In September 2021, Biden's national security adviser Jake Sullivan met in Saudi Arabia with Crown Prince Bin Salman to discuss the high oil prices. The record-high energy prices were driven by a global surge in demand as the world quit the economic recession caused by COVID-19. The Biden administration was pressed on potential oil deals with Saudi Arabia, Venezuela, and Iran that would have them increase their oil production. However, so far, Saudi Arabia and the United Arab Emirates have declined requests from the US.


title: Presidency of Joe Biden

text: As a presidential candidate, Joe Biden had vowed to make the Saudis “pay the price” and make them a “pariah” state, citing the Kingdom's involvement in the assassination of Jamal Khashoggi. But, in June 2022, the White House confirmed that Biden was to visit Saudi Arabia and meet Crown Prince Mohammed bin Salman, during his Middle East trip in July. The announcement came after inflation in the US rose to a 40-year high. The Russian invasion of Ukraine also had an impact on the oil and gas prices in the US. Biden repeatedly appealed to the Saudis to increase oil production, but the Kingdom turned down such requests. Biden's planned visit was seen as a move to seek Saudi assistance to ease the oil and gas prices at home. However, human rights activists and Democratic lawmakers warned Biden that the visit could send signals to Saudi that their horrific human rights violations could be exempted. Saudi dissidents living in the US said that as Saudi activists who were wronged by Prince Mohammed, they “feel betrayed by Biden”. Son of Saad Aljabri, Khalid AlJabri said Biden's meeting with MbS would be “equivalent of a presidential pardon for murder”. Democratic Representative Adam Schiff also criticized the visit saying, “I wouldn't go. I wouldn't shake his hand. This is someone who butchered an American resident, cut him up into pieces and in the most terrible and premeditated way.”


title: Presidency of Joe Biden

text: On 10 July 2022, president Biden defended his trip to Saudi Arabia, saying humans rights were on his agenda. In an op-ed, he wrote that he aims to "reorient and not rupture relations with a country that’s been a strategic partner for 80 years", and that Saudi Arabia has helped to restore unity among the six countries of Gulf Cooperation Council and has fully supported the truce in the context of the Yemen war.


title: Presidency of Joe Biden

text: Ahead of Biden's visit to Saudi Arabia, reports revealed that the Biden administration could possibly lift a ban on sales of Offensive weapons to Riyadh. However, U.S. national security adviser Jake Sullivan they were focused on a “real ceasefire”, and on Saudi efforts to end the war. Following the meeting with Saudi officials, Biden announced that the Kingdom committed to extend the truce in Yemen. On 2 August 2022, the State Department approved the potential sale of 300 MIM-104E Guidance Enhanced Missile-Tactical Ballistic Missiles (GEM-T) for the Patriot missile defense system to Saudi Arabia. It also approved support equipment, spares and technical support to the Arab nation. In addition, the State Department also approved the potential sale of 96 Terminal High Altitude Area Defense (THAAD) missile defense system interceptors and support equipment to the UAE. However, Human Rights Watch said the US should suspend sales of both offensive and defensive arms to Saudi Arabia and the UAE, which have used American weapons in unlawful airstrikes. HRW said a policy reversal by the US could lead to added rights violations in Yemen.


title: Presidency of Joe Biden

text: The U.S. authorities indicted Thomas J. Barrack Jr., an outside adviser to Donald Trump during and after the 2016 United States presidential election campaign. They alleged he acted as an unregistered foreign lobbyist for the United Arab Emirates. Barrack was also accused of obstruction of justice by giving false statements to the investigators. He was found not guilty on all charges in November 2022. The DOJ also prosecuted some men for funneling more than $3.5 million to Hillary Clinton from George Nader, the royal adviser of the UAE.


title: Presidency of Joe Biden

text: While federal prosecutors accused the Emirates of interfering in American politics from both sides, the relations with the Arab nation during Biden's presidency didn't witness much of the expected changes. The UAE was seen escaping its blunder-filled history of relations with the US, despite Biden's repetitive criticism against the Emirates' human rights violations and its attempts of infiltrating the US politics. Moreover, the Biden administration also permitted the arms sales of $23 billion to the UAE, which was initiated by Donald Trump and involved a transfer of sophisticated weaponry like the F-35 fighter jets. The US Justice Department did not charge any Emirati in the case. However, Barrack's indictment identified three UAE officials who were hosts at his reception in the Gulf nation after Trump's 2016 elections, and two others who were involved. Amongst the hosts was Abu Dhabi Crown Prince Mohamed bin Zayed, the UAE's national security adviser Tahnoun bin Zayed and director of the Emirati intelligence service, Ali Mohammed Hammad Al Shamsi. The fourth Emirati official was Abdullah Khalifa Al Ghafli, who “tasked” Barrack to push Emirati interests with America. Another official was Yousef Al Otaiba, who asked to remain anonymous in discussions over private matters.


title: Presidency of Joe Biden

text: Early in the Biden administration, the White House confirmed that the U.S. Embassy would remain in Jerusalem, which would remain recognized as the Capital. The administration also expressed support for the Abraham Accords while wanting to expand on them, although it shied away from using that name, instead referring to it simply as "the normalization process".


title: Presidency of Joe Biden

text: On 13 May 2021, in the aftermath of the Al-Aqsa mosque conflict, the Biden administration was accused of being indifferent towards the violent conflict between Israeli statehood and the Palestinian minority there. Critics on both sides identified the reaction by the White House as "lame and late".


title: Presidency of Joe Biden

text: On 21 May 2021, a ceasefire was brokered between Israel and Hamas after eleven days of clashes. According to Biden, the US will be playing a key role to rebuild damaged infrastructure in the Gaza alongside the Palestinian authority.


title: Presidency of Joe Biden

text: During a July 2022 visit to Israel, Biden stressed the importance of keeping the two-state vision alive. He met with Palestinian National Authority President Mahmoud Abbas and announced a new aid package to the Palestinians. During the administration of his predecessor Donald Trump, U.S. contributions to the United Nations Relief and Works Agency for Palestine Refugees had been defunded. On the Israeli end, Prime Minister Yair Lapid reaffirmed his position on a two-state solution.


title: Presidency of Joe Biden

text: On February 4, 2021, Biden issued a presidential memorandum for expanding protection of LGBT rights worldwide, which includes the possibility to impose financial sanctions.


title: Presidency of Joe Biden

text: Despite Biden's low approvals, a red wave did not occur during the president's first midterm as many had anticipated. Democrats expanded their narrow Senate majority while Republicans took control of the House of Representatives by a far smaller margin than expected. This was largely attributed to a backlash against the Supreme Court's decision in Dobbs v. Jackson Women's Health Organization, as well as the perceived extremeness of certain Republican candidates in competitive races.


title: Presidency of Joe Biden

text: It was the first midterm election since 1986 in which the party of the incumbent president achieved a net gain in governorships, and the first since 1934 in which the president's party didn't lose any state legislative chambers or incumbent senators.


title: Presidency of Joe Biden

text: Many pollsters and pundits had failed to predict the Democrats' resilient performance; Simon Rosenberg was one exception. Republican pollsters such as the Trafalgar Group had a notable polling miss, with errors far outside the margin of error in races such as the senate races in Washington, Colorado, and New Hampshire.


title: Presidency of Joe Biden

text: The results drew praise from the Democratic Party, and Biden celebrated the results as a strong day for democracy.


title: Presidency of Joe Biden

text: Biden's age and low approvals have led some to speculate that he may not run for re-election in 2024, though Biden has indicated his intent to run, with his final announcement expected in 2023.


title: Presidency of Joe Biden

text: Very early in Biden's presidency, opinion polls found that Biden's approval ratings were steadier than Trump's, with an average approval rating of 55% and an average disapproval rate of 39%. Biden's early approval ratings have been more polarized than Trump's, with 98% of Democrats, 61% of independents and 11% of Republicans approving of Biden's presidency in February 2021, a party gap of 87%. Around the end of his first hundred days in office, Biden's approval rating was higher than Trump's but was the third worst since the presidency of Harry Truman; only Trump and Gerald Ford scored lower.


title: Presidency of Joe Biden

text: Following the fall of Kabul and the surge of COVID-19 cases due to the Delta variant in July and August 2021, Biden's approval rating began to steadily decline, from a high of 52.7% approval on July 26, 2021, to 45.9% approval by September 3, 2021, according to FiveThirtyEight. While the White House emphasized COVID-19 as causing his low approval rating, inflation, the highest in nearly 40 years, has also been described as a cause. Biden's lowest approval rating on record comes from a Quinnipiac University poll in July 2022, which showed just 31% of respondents approving of his performance as president.


title: Presidency of Joe Biden

text: By the one-year anniversary of Biden's presidency on January 20, 2022, Gallup recorded the average approval rating for Biden's first year as 49%, which was the second-lowest first-year average approval rating for any American president since World War II; only Trump's first-year average of 38.4% was lower. Gallup further noted that there was greater political polarization in Biden's approval ratings than any other first-year president in modern history, with 91% of Democrats supporting Biden while just 8% of Republicans supported him, resulting in a party gap of 83%. The only other year of any presidency that saw greater polarization was Trump's final year in office. The July 2022 Gallup survey saw Biden's sixth quarter approval rating of 40%, the lowest sixth quarter rating of any president in modern history dating back to Dwight Eisenhower.


title: Methane

text: Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth makes it an economically attractive fuel, although capturing and storing it poses technical challenges due to its gaseous state under normal conditions for temperature and pressure.


title: Methane

text: Naturally occurring methane is found both below ground and under the seafloor and is formed by both geological and biological processes. The largest reservoir of methane is under the seafloor in the form of methane clathrates. When methane reaches the surface and the atmosphere, it is known as atmospheric methane. The Earth's atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases. It has also been detected on other planets, including Mars, which has implications for astrobiology research.


title: Methane

text: Methane is a tetrahedral molecule with four equivalent C–H bonds. Its electronic structure is described by four bonding molecular orbitals (MOs) resulting from the overlap of the valence orbitals on C and H. The lowest-energy MO is the result of the overlap of the 2s orbital on carbon with the in-phase combination of the 1s orbitals on the four hydrogen atoms. Above this energy level is a triply degenerate set of MOs that involve overlap of the 2p orbitals on carbon with various linear combinations of the 1s orbitals on hydrogen. The resulting "three-over-one" bonding scheme is consistent with photoelectron spectroscopic measurements.


title: Methane

text: Methane is an odorless gas and appears to be colorless. It does absorb visible light especially at the red end of the spectrum due to overtone bands, but the effect is only noticeable if the light path is very long. This is what gives Uranus and Neptune their blue or bluish-green colors, as light passes through their atmospheres containing methane and is then scattered back out.


title: Methane

text: The familiar smell of natural gas as used in homes is achieved by the addition of an odorant, usually blends containing tert-butylthiol, as a safety measure. Methane has a boiling point of −161.5 °C at a pressure of one atmosphere. As a gas, it is flammable over a range of concentrations (5.4–17%) in air at standard pressure.


title: Methane

text: Solid methane exists in several modifications. Presently nine are known. Cooling methane at normal pressure results in the formation of methane I. This substance crystallizes in the cubic system (space group Fmm). The positions of the hydrogen atoms are not fixed in methane I, i.e. methane molecules may rotate freely. Therefore, it is a plastic crystal.


title: Methane

text: The primary chemical reactions of methane are combustion, steam reforming to syngas, and halogenation. In general, methane reactions are difficult to control.


title: Methane

text: Partial oxidation of methane to methanol, a more convenient, liquid fuel, is challenging because the reaction typically progresses all the way to carbon dioxide and water even with an insufficient supply of oxygen. The enzyme methane monooxygenase produces methanol from methane, but cannot be used for industrial-scale reactions. Some homogeneously catalyzed systems and heterogeneous systems have been developed, but all have significant drawbacks. These generally operate by generating protected products which are shielded from overoxidation. Examples include the Catalytica system, copper zeolites, and iron zeolites stabilizing the alpha-oxygen active site.


title: Methane

text: One group of bacteria catalyze methane oxidation with nitrite as the oxidant in the absence of oxygen, giving rise to the so-called anaerobic oxidation of methane.


title: Methane

text: Like other hydrocarbons, methane is an extremely weak acid. Its pK in DMSO is estimated to be 56. It cannot be deprotonated in solution, but the conjugate base is known in forms such as methyllithium.


title: Methane

text: A variety of positive ions derived from methane have been observed, mostly as unstable species in low-pressure gas mixtures. These include methenium or methyl cation , methane cation , and methanium or protonated methane . Some of these have been detected in outer space. Methanium can also be produced as diluted solutions from methane with superacids. Cations with higher charge, such as and , have been studied theoretically and conjectured to be stable.


title: Methane

text: Despite the strength of its C–H bonds, there is intense interest in catalysts that facilitate C–H bond activation in methane (and other lower numbered alkanes).


title: Methane

text: Methane's heat of combustion is 55.5 MJ/kg. Combustion of methane is a multiple step reaction summarized as follows:


title: Methane

text: Peters four-step chemistry is a systematically reduced four-step chemistry that explains the burning of methane.


title: Methane

text: where X is a halogen: fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). This mechanism for this process is called free radical halogenation. It is initiated when UV light or some other radical initiator (like peroxides) produces a halogen atom. A two-step chain reaction ensues in which the halogen atom abstracts a hydrogen atom from a methane molecule, resulting in the formation of a hydrogen halide molecule and a methyl radical (CH•). The methyl radical then reacts with a molecule of the halogen to form a molecule of the halomethane, with a new halogen atom as byproduct. Similar reactions can occur on the halogenated product, leading to replacement of additional hydrogen atoms by halogen atoms with dihalomethane, trihalomethane, and ultimately, tetrahalomethane structures, depending upon reaction conditions and the halogen-to-methane ratio.


title: Methane

text: Methane is used in industrial chemical processes and may be transported as a refrigerated liquid (liquefied natural gas, or LNG). While leaks from a refrigerated liquid container are initially heavier than air due to the increased density of the cold gas, the gas at ambient temperature is lighter than air. Gas pipelines distribute large amounts of natural gas, of which methane is the principal component.


title: Methane

text: Methane is used as a fuel for ovens, homes, water heaters, kilns, automobiles, turbines, etc. Activated carbon is used to store methane. Refined liquid methane is used as a rocket fuel, when combined with liquid oxygen, as in the BE-4 and Raptor engines.


title: Methane

text: As the major constituent of natural gas, methane is important for electricity generation by burning it as a fuel in a gas turbine or steam generator. Compared to other hydrocarbon fuels, methane produces less carbon dioxide for each unit of heat released. At about 891 kJ/mol, methane's heat of combustion is lower than that of any other hydrocarbon, but the ratio of the heat of combustion (891 kJ/mol) to the molecular mass (16.0 g/mol, of which 12.0 g/mol is carbon) shows that methane, being the simplest hydrocarbon, produces more heat per mass unit (55.7 kJ/g) than other complex hydrocarbons. In many cities, methane is piped into homes for domestic heating and cooking. In this context it is usually known as natural gas, which is considered to have an energy content of 39 megajoules per cubic meter, or 1,000 BTU per standard cubic foot. Liquefied natural gas (LNG) is predominantly methane (CH) converted into liquid form for ease of storage or transport.


title: Methane

text: As a liquid rocket fuel, methane offers the advantage over kerosene of producing small exhaust molecules. This deposits less soot on the internal parts of rocket motors, reducing the difficulty of booster re-use. The lower molecular weight of the exhaust also increases the fraction of the heat energy which is in the form of kinetic energy available for propulsion, increasing the specific impulse of the rocket. Liquid methane also has a temperature range (91–112 K) nearly compatible with liquid oxygen (54–90 K).


title: Methane

text: Natural gas, which is mostly composed of methane, is used to produce hydrogen gas on an industrial scale. Steam methane reforming (SMR), or simply known as steam reforming, is the standard industrial method of producing commercial bulk hydrogen gas. More than 50 million metric tons are produced annually worldwide (2013), principally from the SMR of natural gas. Much of this hydrogen is used in petroleum refineries, in the production of chemicals and in food processing. Very large quantities of hydrogen are used in the industrial synthesis of ammonia.


title: Methane

text: At high temperatures (700–1100 °C) and in the presence of a metal-based catalyst (nickel), steam reacts with methane to yield a mixture of CO and H, known as "water gas" or "syngas":


title: Methane

text: Methane is also subjected to free-radical chlorination in the production of chloromethanes, although methanol is a more typical precursor.


title: Methane

text: Hydrogen can also be produced via the direct decomposition of methane, also known as methane Pyrolysis. Methane decomposition is a promising route for low-emission hydrogen production since no direct carbon emissions are produced unlike steam methane reforming. Temperatures in excess of 1200 °C are required to break the bonds of methane to produce Hydrogen gas and solid carbon. However, through the use of a suitable catalyst the reaction temperature can be reduced to between 600 °C - 1000 °C depending on the chosen catalyst. The reaction is moderately endothermic as shown in the reaction equation below.


title: Methane

text: The two main routes for geological methane generation are (i) organic (thermally generated, or thermogenic) and (ii) inorganic (abiotic). Thermogenic methane occurs due to the breakup of organic matter at elevated temperatures and pressures in deep sedimentary strata. Most methane in sedimentary basins is thermogenic; therefore, thermogenic methane is the most important source of natural gas. Thermogenic methane components are typically considered to be relic (from an earlier time). Generally, formation of thermogenic methane (at depth) can occur through organic matter breakup, or organic synthesis. Both ways can involve microorganisms (methanogenesis), but may also occur inorganically. The processes involved can also consume methane, with and without microorganisms.


title: Methane

text: The more important source of methane at depth (crystalline bedrock) is abiotic. Abiotic means that methane is created from inorganic compounds, without biological activity, either through magmatic processes or via water-rock reactions that occur at low temperatures and pressures, like serpentinization.


title: Methane

text: Most of Earth's methane is biogenic and is produced by methanogenesis, a form of anaerobic respiration only known to be conducted by some members of the domain Archaea. Methanogens occupy landfills and other soils, ruminants (for example, cattle), the guts of termites, and the anoxic sediments below the seafloor and the bottom of lakes. Rice fields also generate large amounts of methane during plant growth. This multistep process is used by these microorganisms for energy. The net reaction of methanogenesis is:


title: Methane

text: Ruminants, such as cattle, belch methane, accounting for about 22% of the U.S. annual methane emissions to the atmosphere. One study reported that the livestock sector in general (primarily cattle, chickens, and pigs) produces 37% of all human-induced methane. A 2013 study estimated that livestock accounted for 44% of human-induced methane and about 15% of human-induced greenhouse gas emissions. Many efforts are underway to reduce livestock methane production, such as medical treatments and dietary adjustments, and to trap the gas to use its combustion energy.


title: Methane

text: Most of the subseafloor is anoxic because oxygen is removed by aerobic microorganisms within the first few centimeters of the sediment. Below the oxygen-replete seafloor, methanogens produce methane that is either used by other organisms or becomes trapped in gas hydrates. These other organisms that utilize methane for energy are known as methanotrophs ('methane-eating'), and are the main reason why little methane generated at depth reaches the sea surface. Consortia of Archaea and Bacteria have been found to oxidize methane via anaerobic oxidation of methane (AOM); the organisms responsible for this are anaerobic methanotrophic Archaea (ANME) and sulfate-reducing bacteria (SRB).


title: Methane

text: Given its cheap abundance in natural gas, there is little incentive to produce methane industrially. Methane can be produced by hydrogenating carbon dioxide through the Sabatier process. Methane is also a side product of the hydrogenation of carbon monoxide in the Fischer–Tropsch process, which is practiced on a large scale to produce longer-chain molecules than methane.


title: Methane

text: An example of large-scale coal-to-methane gasification is the Great Plains Synfuels plant, started in 1984 in Beulah, North Dakota as a way to develop abundant local resources of low-grade lignite, a resource that is otherwise difficult to transport for its weight, ash content, low calorific value and propensity to spontaneous combustion during storage and transport. A number of similar plants exist around the world, although mostly these plants are targeted towards the production of long chain alkanes for use as gasoline, diesel, or feedstock to other processes.


title: Methane

text: Power to methane is a technology that uses electrical power to produce hydrogen from water by electrolysis and uses the Sabatier reaction to combine hydrogen with carbon dioxide to produce methane. As of 2021, this is mostly under development and not in large-scale use. Theoretically, the process could be used as a buffer for excess and off-peak power generated by highly fluctuating wind turbines and solar arrays. However, as currently very large amounts of natural gas are used in power plants (e.g. CCGT) to produce electric energy, the losses in efficiency are not acceptable.


title: Methane

text: Methane can be produced by protonation of methyl lithium or a methyl Grignard reagent such as methylmagnesium chloride. It can also be made from anhydrous sodium acetate and dry sodium hydroxide, mixed and heated above 300 °C (with sodium carbonate as byproduct). In practice, a requirement for pure methane can easily be fulfilled by steel gas bottle from standard gas suppliers.


title: Methane

text: Methane was discovered and isolated by Alessandro Volta between 1776 and 1778 when studying marsh gas from Lake Maggiore. It is the major component of natural gas, about 87% by volume. The major source of methane is extraction from geological deposits known as natural gas fields, with coal seam gas extraction becoming a major source (see coal bed methane extraction, a method for extracting methane from a coal deposit, while enhanced coal bed methane recovery is a method of recovering methane from non-mineable coal seams). It is associated with other hydrocarbon fuels, and sometimes accompanied by helium and nitrogen. Methane is produced at shallow levels (low pressure) by anaerobic decay of organic matter and reworked methane from deep under the Earth's surface. In general, the sediments that generate natural gas are buried deeper and at higher temperatures than those that contain oil.


title: Methane

text: Methane is generally transported in bulk by pipeline in its natural gas form, or by LNG carriers in its liquefied form; few countries transport it by truck.


title: Methane

text: In 2010, methane levels in the Arctic were measured at 1850 nmol/mol. This level is over twice as high as at any time in the last 400,000 years. Historic methane concentrations in the world's atmosphere have ranged between 300 and 400 nmol/mol during glacial periods commonly known as ice ages, and between 600 and 700 nmol/mol during the warm interglacial periods. The Earth's oceans are a potential important source of Arctic methane.


title: Methane

text: Methane is an important greenhouse gas with a global warming potential of 34 compared to CO (potential of 1) over a 100-year period, and 72 over a 20-year period.


title: Methane

text: The Earth's atmospheric methane concentration has increased by about 150% since 1750, and it accounts for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases. The AR6 of the IPCC states: "Observed increases in well-mixed greenhouse gas (GHG) concentrations since around 1750 are unequivocally caused by human activities. Since 2011 (measurements reported in AR5), concentrations have continued to increase in the atmosphere, reaching annual averages of 410 ppm for carbon dioxide (CO), 1866 ppb for methane (CH), and 332 ppb for nitrous oxide (NO) in 2019. (…) In 2019, atmospheric CO concentrations were higher than at any time in at least 2 million years (high confidence), and concentrations of CH and NO were higher than at any time in at least 800,000 years (very high confidence). Since 1750, increases in CO (47%) and CH (156%) concentrations far exceed, and increases in NO (23%) are similar to, the natural multi-millennial changes between glacial and interglacial periods over at least the past 800,000 years (very high confidence)".


title: Methane

text: From 2015 to 2019 sharp rises in levels of atmospheric methane have been recorded. In February 2020, it was reported that fugitive emissions and gas venting from the fossil fuel industry may have been significantly underestimated.


title: Methane

text: Climate change can increase atmospheric methane levels by increasing methane production in natural ecosystems, forming a Climate change feedback. Another explanation for the rise in methane emissions could be a slowdown of the chemical reaction that removes methane from the atmosphere.


title: Methane

text: Methane clathrates (also known as methane hydrates) are solid cages of water molecules that trap single molecules of methane. Significant reservoirs of methane clathrates have been found in arctic permafrost and along continental margins beneath the ocean floor within the gas clathrate stability zone, located at high pressures (1 to 100 MPa; lower end requires lower temperature) and low temperatures (< 15 °C; upper end requires higher pressure). Methane clathrates can form from biogenic methane, thermogenic methane, or a mix of the two. These deposits are both a potential source of methane fuel as well as a potential contributor to global warming. The global mass of carbon stored in gas clathrates is still uncertain and has been estimated as high as 12,500 Gt carbon and as low as 500 Gt carbon. The estimate has declined over time with a most recent estimate of ~1800 Gt carbon. A large part of this uncertainty is due to our knowledge gap in sources and sinks of methane and the distribution of methane clathrates at the global scale. For example, a source of methane was discovered relatively recently in an ultraslow spreading ridge in the Arctic. Some climate models suggest that today's methane emission regime from the ocean floor is potentially similar to that during the period of the Paleocene–Eocene Thermal Maximum (PETM) around 55.5 million years ago, although there are no data indicating that methane from clathrate dissociation currently reaches the atmosphere. Arctic methane release from permafrost and seafloor methane clathrates is a potential consequence and further cause of global warming; this is known as the clathrate gun hypothesis. Data from 2016 indicate that Arctic permafrost thaws faster than predicted.


title: Methane

text: Methane is abundant in many parts of the Solar System and potentially could be harvested on the surface of another solar-system body (in particular, using methane production from local materials found on Mars or Titan), providing fuel for a return journey.


title: Methane

text: Methane has been detected on all planets of the Solar System and most of the larger moons. With the possible exception of Mars, it is believed to have come from abiotic processes.


title: Methane

text: The "Curiosity" rover has documented seasonal fluctuations of atmospheric methane levels on Mars. These fluctuations peaked at the end of the Martian summer at 0.6 parts per billion.


title: Methane

text: Methane has been proposed as a possible rocket propellant on future Mars missions due in part to the possibility of synthesizing it on the planet by in situ resource utilization. An adaptation of the Sabatier methanation reaction may be used with a mixed catalyst bed and a reverse water-gas shift in a single reactor to produce methane from the raw materials available on Mars, utilizing water from the Martian subsoil and carbon dioxide in the Martian atmosphere.


title: Methane

text: Methane could be produced by a non-biological process called serpentinization involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars.


title: Methane

text: In November 1776, methane was first scientifically identified by Italian physicist Alessandro Volta in the marshes of Lake Maggiore straddling Italy and Switzerland. Volta was inspired to search for the substance after reading a paper written by Benjamin Franklin about "flammable air". Volta collected the gas rising from the marsh, and by 1778 had isolated pure methane. He also demonstrated that the gas could be ignited with an electric spark.


title: Methane

text: Following the Felling mine disaster of 1812 in which 92 men perished, Sir Humphry Davy established that the feared firedamp was in fact largely methane.


title: Methane

text: The name "methane" was coined in 1866 by the German chemist August Wilhelm von Hofmann. The name was derived from methanol.


title: Methane

text: Etymologically, the word "methane" is coined from the chemical suffix ""-ane"", which denotes substances belonging to the alkane family; and the word "methyl", which is derived from the German (1840) or directly from the French , which is a back-formation from the French (corresponding to English "methylene"), the root of which was coined by Jean-Baptiste Dumas and Eugène Péligot in 1834 from the Greek (wine) (related to English "mead") and (meaning "wood"). The radical is named after this because it was first detected in methanol, an alcohol first isolated by distillation of wood. The chemical suffix "-ane" is from the coordinating chemical suffix "-ine" which is from Latin feminine suffix "-ina" which is applied to represent abstracts. The coordination of "-ane", "-ene", "-one", etc. was proposed in 1866 by German chemist August Wilhelm von Hofmann (1818–1892).


title: Methane

text: The abbreviation CH-C can mean the mass of carbon contained in a mass of methane, and the mass of methane is always 1.33 times the mass of CH-C. CH-C can also mean the methane-carbon ratio, which is 1.33 by mass. Methane at scales of the atmosphere is commonly measured in teragrams (Tg CH) or millions of metric tons (MMT CH), which mean the same thing. Other standard units are also used, such as nanomole (nmol, one billionth of a mole), mole (mol), kilogram, and gram.


title: Methane

text: Methane is nontoxic, yet it is extremely flammable and may form explosive mixtures with air. Methane is also an asphyxiant if the oxygen concentration is reduced to below about 16% by displacement, as most people can tolerate a reduction from 21% to 16% without ill effects. The concentration of methane at which asphyxiation risk becomes significant is much higher than the 5–15% concentration in a flammable or explosive mixture. Methane off-gas can penetrate the interiors of buildings near landfills and expose occupants to significant levels of methane. Some buildings have specially engineered recovery systems below their basements to actively capture this gas and vent it away from the building.


title: Methane

text: Methane gas explosions are responsible for many deadly mining disasters. A methane gas explosion was the cause of the Upper Big Branch coal mine disaster in West Virginia on April 5, 2010, killing 29. Natural gas accidental release has also been a major focus in the field of safety engineering, due to past accidental releases that concluded in the formation of jet fire disasters.


title: Mitochondrion

text: A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used throughout the cell as a source of chemical energy. They were discovered by Albert von Kölliker in 1857 in the voluntary muscles of insects. The term "mitochondrion" was coined by Carl Benda in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase coined by Philip Siekevitz in a 1957 article of the same name.


title: Mitochondrion

text: Some cells in some multicellular organisms lack mitochondria (for example, mature mammalian red blood cells). A large number of unicellular organisms, such as microsporidia, parabasalids and diplomonads, have reduced or transformed their mitochondria into other structures. One eukaryote, "Monocercomonoides", is known to have completely lost its mitochondria, and one multicellular organism, "Henneguya salminicola", is known to have retained mitochondrion-related organelles in association with a complete loss of their mitochondrial genome.


title: Mitochondrion

text: Mitochondria are commonly between 0.75 and 3 μm in crossection, but vary considerably in size and structure. Unless specifically stained, they are not visible. In addition to supplying cellular energy, mitochondria are involved in other tasks, such as signaling, cellular differentiation, and cell death, as well as maintaining control of the cell cycle and cell growth. Mitochondrial biogenesis is in turn temporally coordinated with these cellular processes. Mitochondria have been implicated in several human disorders and conditions, such as mitochondrial diseases, cardiac dysfunction, heart failure and autism.


title: Mitochondrion

text: The number of mitochondria in a cell can vary widely by organism, tissue, and cell type. A mature red blood cell has no mitochondria, whereas a liver cell can have more than 2000. The mitochondrion is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, intermembrane space, inner membrane, cristae, and matrix.


title: Mitochondrion

text: Although most of a eukaryotic cell's DNA is contained in the cell nucleus, the mitochondrion has its own genome ("mitogenome") that is substantially similar to bacterial genomes. This finding has led to general acceptance of the endosymbiotic hypothesis - that free-living prokaryotic ancestors of modern mitochondria permanently fused with eukaryotic cells in the distant past, evolving such that modern animals, plants, fungi, and other eukaryotes are able to respire to generate cellular energy.


title: Mitochondrion

text: A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins. The two membranes have different properties. Because of this double-membraned organization, there are five distinct parts to a mitochondrion:


title: Mitochondrion

text: Mitochondria have folding to increase surface area, which in turn increases ATP (adenosine triphosphate) production.


title: Mitochondrion

text: The outer mitochondrial membrane, which encloses the entire organelle, is 60 to 75 angstroms (Å) thick. It has a protein-to-phospholipid ratio similar to that of the cell membrane (about 1:1 by weight). It contains large numbers of integral membrane proteins called porins. A major trafficking protein is the pore-forming voltage-dependent anion channel (VDAC). The VDAC is the primary transporter of nucleotides, ions and metabolites between the cytosol and the intermembrane space. It is formed as a beta barrel that spans the outer membrane, similar to that in the gram-negative bacterial membrane. Larger proteins can enter the mitochondrion if a signaling sequence at their N-terminus binds to a large multisubunit protein called translocase in the outer membrane, which then actively moves them across the membrane. Mitochondrial pro-proteins are imported through specialised translocation complexes.


title: Mitochondrion

text: The outer membrane also contains enzymes involved in such diverse activities as the elongation of fatty acids, oxidation of epinephrine, and the degradation of tryptophan. These enzymes include monoamine oxidase, rotenone-insensitive NADH-cytochrome c-reductase, kynurenine hydroxylase and fatty acid Co-A ligase. Disruption of the outer membrane permits proteins in the intermembrane space to leak into the cytosol, leading to cell death. The outer mitochondrial membrane can associate with the endoplasmic reticulum (ER) membrane, in a structure called MAM (mitochondria-associated ER-membrane). This is important in the ER-mitochondria calcium signaling and is involved in the transfer of lipids between the ER and mitochondria. Outside the outer membrane are small (diameter: 60 Å) particles named sub-units of Parson.


title: Mitochondrion

text: The mitochondrial intermembrane space is the space between the outer membrane and the inner membrane. It is also known as perimitochondrial space. Because the outer membrane is freely permeable to small molecules, the concentrations of small molecules, such as ions and sugars, in the intermembrane space is the same as in the cytosol. However, large proteins must have a specific signaling sequence to be transported across the outer membrane, so the protein composition of this space is different from the protein composition of the cytosol. One protein that is localized to the intermembrane space in this way is cytochrome c.


title: Mitochondrion

text: It contains more than 151 different polypeptides, and has a very high protein-to-phospholipid ratio (more than 3:1 by weight, which is about 1 protein for 15 phospholipids). The inner membrane is home to around 1/5 of the total protein in a mitochondrion. Additionally, the inner membrane is rich in an unusual phospholipid, cardiolipin. This phospholipid was originally discovered in cow hearts in 1942, and is usually characteristic of mitochondrial and bacterial plasma membranes. Cardiolipin contains four fatty acids rather than two, and may help to make the inner membrane impermeable. Unlike the outer membrane, the inner membrane does not contain porins, and is highly impermeable to all molecules. Almost all ions and molecules require special membrane transporters to enter or exit the matrix. Proteins are ferried into the matrix via the translocase of the inner membrane (TIM) complex or via OXA1L. In addition, there is a membrane potential across the inner membrane, formed by the action of the enzymes of the electron transport chain. Inner membrane fusion is mediated by the inner membrane protein OPA1.


title: Mitochondrion

text: The inner mitochondrial membrane is compartmentalized into numerous folds called cristae, which expand the surface area of the inner mitochondrial membrane, enhancing its ability to produce ATP. For typical liver mitochondria, the area of the inner membrane is about five times as large as the outer membrane. This ratio is variable and mitochondria from cells that have a greater demand for ATP, such as muscle cells, contain even more cristae. Mitochondria within the same cell can have substantially different crista-density, with the ones that are required to produce more energy having much more crista-membrane surface. These folds are studded with small round bodies known as F particles or oxysomes.


title: Mitochondrion

text: The matrix is the space enclosed by the inner membrane. It contains about 2/3 of the total proteins in a mitochondrion. The matrix is important in the production of ATP with the aid of the ATP synthase contained in the inner membrane. The matrix contains a highly concentrated mixture of hundreds of enzymes, special mitochondrial ribosomes, tRNA, and several copies of the mitochondrial DNA genome. Of the enzymes, the major functions include oxidation of pyruvate and fatty acids, and the citric acid cycle. The DNA molecules are packaged into nucleoids by proteins, one of which is TFAM.


title: Mitochondrion

text: The most prominent roles of mitochondria are to produce the energy currency of the cell, ATP (i.e., phosphorylation of ADP), through respiration and to regulate cellular metabolism. The central set of reactions involved in ATP production are collectively known as the citric acid cycle, or the Krebs cycle, and oxidative phosphorylation. However, the mitochondrion has many other functions in addition to the production of ATP.


title: Mitochondrion

text: A dominant role for the mitochondria is the production of ATP, as reflected by the large number of proteins in the inner membrane for this task. This is done by oxidizing the major products of glucose: pyruvate, and NADH, which are produced in the cytosol. This type of cellular respiration, known as aerobic respiration, is dependent on the presence of oxygen. When oxygen is limited, the glycolytic products will be metabolized by anaerobic fermentation, a process that is independent of the mitochondria. The production of ATP from glucose and oxygen has an approximately 13-times higher yield during aerobic respiration compared to fermentation. Plant mitochondria can also produce a limited amount of ATP either by breaking the sugar produced during photosynthesis or without oxygen by using the alternate substrate nitrite. ATP crosses out through the inner membrane with the help of a specific protein, and across the outer membrane via porins. ADP returns via the same route.


title: Mitochondrion

text: Pyruvate molecules produced by glycolysis are actively transported across the inner mitochondrial membrane, and into the matrix where they can either be oxidized and combined with coenzyme A to form CO, acetyl-CoA, and NADH, or they can be carboxylated (by pyruvate carboxylase) to form oxaloacetate. This latter reaction "fills up" the amount of oxaloacetate in the citric acid cycle and is therefore an anaplerotic reaction, increasing the cycle's capacity to metabolize acetyl-CoA when the tissue's energy needs (e.g., in muscle) are suddenly increased by activity.


title: Mitochondrion

text: In the citric acid cycle, all the intermediates (e.g. citrate, iso-citrate, alpha-ketoglutarate, succinate, fumarate, malate and oxaloacetate) are regenerated during each turn of the cycle. Adding more of any of these intermediates to the mitochondrion therefore means that the additional amount is retained within the cycle, increasing all the other intermediates as one is converted into the other. Hence, the addition of any one of them to the cycle has an anaplerotic effect, and its removal has a cataplerotic effect. These anaplerotic and cataplerotic reactions will, during the course of the cycle, increase or decrease the amount of oxaloacetate available to combine with acetyl-CoA to form citric acid. This in turn increases or decreases the rate of ATP production by the mitochondrion, and thus the availability of ATP to the cell.


title: Mitochondrion

text: Acetyl-CoA, on the other hand, derived from pyruvate oxidation, or from the beta-oxidation of fatty acids, is the only fuel to enter the citric acid cycle. With each turn of the cycle one molecule of acetyl-CoA is consumed for every molecule of oxaloacetate present in the mitochondrial matrix, and is never regenerated. It is the oxidation of the acetate portion of acetyl-CoA that produces CO and water, with the energy thus released captured in the form of ATP.


title: Mitochondrion

text: In the liver, the carboxylation of cytosolic pyruvate into intra-mitochondrial oxaloacetate is an early step in the gluconeogenic pathway, which converts lactate and de-aminated alanine into glucose, under the influence of high levels of glucagon and/or epinephrine in the blood. Here, the addition of oxaloacetate to the mitochondrion does not have a net anaplerotic effect, as another citric acid cycle intermediate (malate) is immediately removed from the mitochondrion to be converted to cytosolic oxaloacetate, and ultimately to glucose, in a process that is almost the reverse of glycolysis.


title: Mitochondrion

text: The enzymes of the citric acid cycle are located in the mitochondrial matrix, with the exception of succinate dehydrogenase, which is bound to the inner mitochondrial membrane as part of Complex II. The citric acid cycle oxidizes the acetyl-CoA to carbon dioxide, and, in the process, produces reduced cofactors (three molecules of NADH and one molecule of FADH) that are a source of electrons for the electron transport chain, and a molecule of GTP (which is readily converted to an ATP).


title: Mitochondrion

text: The electrons from NADH and FADH are transferred to oxygen (O) and hydrogen (protons) in several steps via an electron transport chain. NADH and FADH molecules are produced within the matrix via the citric acid cycle and in the cytoplasm by glycolysis. Reducing equivalents from the cytoplasm can be imported via the malate-aspartate shuttle system of antiporter proteins or fed into the electron transport chain using a glycerol phosphate shuttle.


title: Mitochondrion

text: The major energy-releasing reactions that make the mitochondrion the "powerhouse of the cell" occur at protein complexes I, III and IV in the inner mitochondrial membrane (NADH dehydrogenase (ubiquinone), cytochrome c reductase, and cytochrome c oxidase). At complex IV, O reacts with the reduced form of iron in cytochrome c:


title: Mitochondrion

text: releasing a lot of free energy from the reactants without breaking bonds of an organic fuel. The free energy put in to remove an electron from Fe is released at complex III when Fe of cytochrome c reacts to oxidize ubiquinol (QH):


title: Mitochondrion

text: While the reactions are controlled by an electron transport chain, free electrons are not amongst the reactants or products in the three reactions shown and therefore do not affect the free energy released, which is used to pump protons (H) into the intermembrane space. This process is efficient, but a small percentage of electrons may prematurely reduce oxygen, forming reactive oxygen species such as superoxide. This can cause oxidative stress in the mitochondria and may contribute to the decline in mitochondrial function associated with aging.


title: Mitochondrion

text: As the proton concentration increases in the intermembrane space, a strong electrochemical gradient is established across the inner membrane. The protons can return to the matrix through the ATP synthase complex, and their potential energy is used to synthesize ATP from ADP and inorganic phosphate (P). This process is called chemiosmosis, and was first described by Peter Mitchell, who was awarded the 1978 Nobel Prize in Chemistry for his work. Later, part of the 1997 Nobel Prize in Chemistry was awarded to Paul D. Boyer and John E. Walker for their clarification of the working mechanism of ATP synthase.


title: Mitochondrion

text: Under certain conditions, protons can re-enter the mitochondrial matrix without contributing to ATP synthesis. This process is known as "proton leak" or mitochondrial uncoupling and is due to the facilitated diffusion of protons into the matrix. The process results in the unharnessed potential energy of the proton electrochemical gradient being released as heat. The process is mediated by a proton channel called thermogenin, or UCP1. Thermogenin is primarily found in brown adipose tissue, or brown fat, and is responsible for non-shivering thermogenesis. Brown adipose tissue is found in mammals, and is at its highest levels in early life and in hibernating animals. In humans, brown adipose tissue is present at birth and decreases with age.


title: Mitochondrion

text: The concentrations of free calcium in the cell can regulate an array of reactions and is important for signal transduction in the cell. Mitochondria can transiently store calcium, a contributing process for the cell's homeostasis of calcium.


title: Mitochondrion

text: Ca influx to the mitochondrial matrix has recently been implicated as a mechanism to regulate respiratory bioenergetics by allowing the electrochemical potential across the membrane to transiently "pulse" from ΔΨ-dominated to pH-dominated, facilitating a reduction of oxidative stress. In neurons, concomitant increases in cytosolic and mitochondrial calcium act to synchronize neuronal activity with mitochondrial energy metabolism. Mitochondrial matrix calcium levels can reach the tens of micromolar levels, which is necessary for the activation of isocitrate dehydrogenase, one of the key regulatory enzymes of the Krebs cycle.


title: Mitochondrion

text: The relationship between cellular proliferation and mitochondria has been investigated. Tumor cells require ample ATP to synthesize bioactive compounds such as lipids, proteins, and nucleotides for rapid proliferation. The majority of ATP in tumor cells is generated via the oxidative phosphorylation pathway (OxPhos). Interference with OxPhos cause cell cycle arrest suggesting that mitochondria play a role in cell proliferation. Mitochondrial ATP production is also vital for cell division and differentiation in infection in addition to basic functions in the cell including the regulation of cell volume, solute concentration, and cellular architecture. ATP levels differ at various stages of the cell cycle suggesting that there is a relationship between the abundance of ATP and the cell's ability to enter a new cell cycle. ATP's role in the basic functions of the cell make the cell cycle sensitive to changes in the availability of mitochondrial derived ATP. The variation in ATP levels at different stages of the cell cycle support the hypothesis that mitochondria play an important role in cell cycle regulation. Although the specific mechanisms between mitochondria and the cell cycle regulation is not well understood, studies have shown that low energy cell cycle checkpoints monitor the energy capability before committing to another round of cell division.


title: Mitochondrion

text: Some mitochondrial functions are performed only in specific types of cells. For example, mitochondria in liver cells contain enzymes that allow them to detoxify ammonia, a waste product of protein metabolism. A mutation in the genes regulating any of these functions can result in mitochondrial diseases.


title: Mitochondrion

text: Mitochondrial proteins (proteins transcribed from mitochondrial DNA) vary depending on the tissue and the species. In humans, 615 distinct types of proteins have been identified from cardiac mitochondria, whereas in rats, 940 proteins have been reported. The mitochondrial proteome is thought to be dynamically regulated.


title: Mitochondrion

text: Mitochondria (or related structures) are found in all eukaryotes (except the Oxymonad "Monocercomonoides"). Although commonly depicted as bean-like structures they form a highly dynamic network in the majority of cells where they constantly undergo fission and fusion. The population of all the mitochondria of a given cell constitutes the chondriome. Mitochondria vary in number and location according to cell type. A single mitochondrion is often found in unicellular organisms, while human liver cells have about 1000–2000 mitochondria per cell, making up 1/5 of the cell volume. The mitochondrial content of otherwise similar cells can vary substantially in size and membrane potential, with differences arising from sources including uneven partitioning at cell division, leading to extrinsic differences in ATP levels and downstream cellular processes. The mitochondria can be found nestled between myofibrils of muscle or wrapped around the sperm flagellum. Often, they form a complex 3D branching network inside the cell with the cytoskeleton. The association with the cytoskeleton determines mitochondrial shape, which can affect the function as well: different structures of the mitochondrial network may afford the population a variety of physical, chemical, and signalling advantages or disadvantages. Mitochondria in cells are always distributed along microtubules and the distribution of these organelles is also correlated with the endoplasmic reticulum. Recent evidence suggests that vimentin, one of the components of the cytoskeleton, is also critical to the association with the cytoskeleton.


title: Mitochondrion

text: The mitochondria-associated ER membrane (MAM) is another structural element that is increasingly recognized for its critical role in cellular physiology and homeostasis. Once considered a technical snag in cell fractionation techniques, the alleged ER vesicle contaminants that invariably appeared in the mitochondrial fraction have been re-identified as membranous structures derived from the MAM—the interface between mitochondria and the ER. Physical coupling between these two organelles had previously been observed in electron micrographs and has more recently been probed with fluorescence microscopy. Such studies estimate that at the MAM, which may comprise up to 20% of the mitochondrial outer membrane, the ER and mitochondria are separated by a mere 10–25 nm and held together by protein tethering complexes.


title: Mitochondrion

text: Purified MAM from subcellular fractionation is enriched in enzymes involved in phospholipid exchange, in addition to channels associated with Ca signaling. These hints of a prominent role for the MAM in the regulation of cellular lipid stores and signal transduction have been borne out, with significant implications for mitochondrial-associated cellular phenomena, as discussed below. Not only has the MAM provided insight into the mechanistic basis underlying such physiological processes as intrinsic apoptosis and the propagation of calcium signaling, but it also favors a more refined view of the mitochondria. Though often seen as static, isolated 'powerhouses' hijacked for cellular metabolism through an ancient endosymbiotic event, the evolution of the MAM underscores the extent to which mitochondria have been integrated into overall cellular physiology, with intimate physical and functional coupling to the endomembrane system.


title: Mitochondrion

text: The MAM is enriched in enzymes involved in lipid biosynthesis, such as phosphatidylserine synthase on the ER face and phosphatidylserine decarboxylase on the mitochondrial face. Because mitochondria are dynamic organelles constantly undergoing fission and fusion events, they require a constant and well-regulated supply of phospholipids for membrane integrity. But mitochondria are not only a destination for the phospholipids they finish synthesis of; rather, this organelle also plays a role in inter-organelle trafficking of the intermediates and products of phospholipid biosynthetic pathways, ceramide and cholesterol metabolism, and glycosphingolipid anabolism.