Usually, this process uses oxygen, and is called aerobic respiration. It has four stages known as glycolysis, Link reaction, the Krebs cycle, and the electron transport chain. This produces ATP which supplies the energy that cells need to do work.
When they do not get enough oxygen, the cells use anaerobic respiration, which does not use oxygen. However, this process produces lactic acid, and is not as efficient as when oxygen is used.
Aerobic respiration, the process that does use oxygen, produces much more energy and does not produce lactic acid. It also produces carbon dioxide as a waste product, which then enters the circulatory system. The carbon dioxide is taken to the lungs, where it is exchanged for oxygen.
The simplified formula for aerobic cellular respiration is:
CHO + 6O → 6CO + 6HO + Energy (as ATP)
The word equation for this is:Glucose (sugar) + Oxygen → Carbon dioxide + Water + Energy (as ATP)
Aerobic cellular respiration has four stages. Each is important, and could not happen without the one before it. The steps of aerobic cellular respiration are:
In glycolysis, glucose in the cytoplasm is broken into two molecules of pyruvate. Ten enzymes are needed for the ten intermediate compounds in this process.
Biology textbooks often state that 38 ATP molecules can be made per oxidised glucose molecule during cellular respiration (two from glycolysis, two from the Krebs cycle, and about 34 from the electron transport chain). However, the process actually makes less energy (ATP) because of losses through leaky membranes. Estimates are 29 to 30 ATP per glucose.
Aerobic metabolism is about (see sentence above) 15 times more efficient than anaerobic metabolism. Anaerobic metabolism yields 2 mol ATP per 1 mol glucose. They share the initial pathway of glycolysis but aerobic metabolism continues with the Krebs cycle and oxidative phosphorylation. The post glycolytic reactions take place in the mitochondria in eukaryotic cells, and in the cytoplasm in prokaryotic cells.
Pyruvate from glycolysis is actively pumped into mitochondria. One carbon dioxide molecule and one hydrogen molecule are removed from the pyruvate (called oxidative decarboxylation) to produce an acetyl group, which joins to an enzyme called CoA to form acetyl CoA. This is essential for the Krebs cycle.
Acetyl CoA joins with oxaloacetate to form a compound with six carbon atoms. This is the first step in the ever-repeating Krebs cycle. Because two acetyl-CoA molecules are produced from each glucose molecule, "two cycles are required per glucose molecule". Therefore, at the end of two cycles, the products are: two ATP, six NADH, two FADH, and four CO2. The ATP is a molecule which carries energy in chemical form to be used in other cell processes. This process is also known as the TCA cycle (Tricarboxylic (try-car-box-ILL-ick) acid cycle), the citric acid cycle, or the Krebs cycle after the biochemist who elucidated its reactions.
This is where most of the ATP is made. All of the hydrogen molecules which have been removed in the steps before (Krebs cycle, Link reaction) are pumped inside the mitochondria using energy that electrons release. Eventually, the electrons powering the pumping of hydrogen into the mitochondria mix with some hydrogen and oxygen to form water and the hydrogen molecules stop being pumped.
Eventually, the hydrogen flows back into the cytoplasm of the mitochondria through protein channels. As the hydrogen flows, ATP is made from ADP and phosphate ions.
Lesotho
Lesotho is a small country in southern Africa. Its population is about 1,800,000.
The capital of Lesotho is called Maseru.
Lesotho has the highest suicide rate in Africa.
Lesotho has no coast on the sea nor on a lake. This type of country is called "landlocked", meaning it is surrounded by land. All of Lesotho's trade must either be flown in by aeroplane, or brought in by land. Lesotho's position is unusual: it is completely surrounded by South Africa and has no borders with any other country. This type of country is called an "enclave". Lesotho is one of the only three enclaved countries in the world (the other two are San Marino and the Vatican City). This makes Lesotho's relationship with South Africa very important to them both.
Lesotho has many mountains and is one of the most mountainous countries in the world. All of Lesotho is at least 1,400 m above sea level. People sometimes travel there to ski in winter. The many mountains in Lesotho mean that it rains there a lot. Lesotho uses some of its water to generate electricity and sells some of the water to South Africa.
Lesotho became a country in 1818, but it was then called Basutoland. A man called Moshoeshoe brought several of the groups of people in the area together and formed a new country with him as its king. This new country came under attack from its enemies and in 1868 Moshoeshoe asked Queen Victoria of Great Britain for help. Great Britain said it would help if Lesotho became part of the British Empire.
Lesotho eventually gained its independence on 4 October 1966. Now it is a member of the British Commonwealth. King Letsie III is the ruler of Lesotho.
Alexander Hamilton
Alexander Hamilton (January 11, 1755 – July 12, 1804) was a statesman, a political theorist and an economist. He was one of the Founding Fathers of the United States. Hamilton was the United States' first Secretary of the Treasury. He was known for the creation of a national bank. Born on the island of Nevis in the Caribbean, Hamilton moved to New York City. When the American Revolutionary War started, Hamilton served in the Continental Army. He was a close aide to General George Washington. After leaving the military he started a bank. He was one of the framers of the United States Constitution. Along with James Madison and John Jay, he wrote the Federalist Papers, which supported the new Constitution.
Hamilton became the Secretary of the Treasury under George Washington. He helped set up the United States' financial system. Hamilton supported a national bank as well as the funding of the national debt. A leader of the Federalist Party, he was a long time rival of Thomas Jefferson. He was killed in a duel with political rival Aaron Burr in 1804.
Today, Hamilton is usually thought of as one of the most important of the early leaders. Hamilton's portrait appears on the United States ten-dollar bill.
Hamilton was not born in the United States. He was from the Caribbean island of Nevis. His father was James Hamilton and his mother was Rachel Fawcett Lavien. Hamilton's mother had a child from a previous marriage that she left behind when she moved to Nevis. At the time, she was still married to another man. This meant that Hamilton was illegitimate. He was very sensitive about this fact. His father had left him as a child. Two years after this tragedy both Hamilton and his mother became sick. Hamilton recovered, but unfortunately his mother died. He was grief-stricken and moved in with his cousin. His cousin committed suicide.
In 1772 Hamilton went to New York to continue his education. He attended Kings College, now called Columbia University, until 1776.
Early in the American Revolution Hamilton was an artillery officer. Later he served on George Washington's staff. Hamilton believed by the late 1780s that the Articles of Confederation made a government that was too weak to work well, and he supported drafting a new document. He was a delegate to the Constitutional Convention, and he was a signer of the Constitution. In 1789 he was co-author of the Federalist Papers, a series of letters written by Hamilton, John Jay, and James Madison under the name "Publius." Hamilton wrote about two-thirds of the essays. They were published in newspapers in New York and supported the new Constitution. These writings are usually thought of as being one of the most important American works on politics and government. They are still widely read today.