*Question*
Q: What is the term for a solution that resists dramatic changes in ph? Read this paragraph and choose the correct option from the provided answers: As indicated in Section 12.4 "Strong and Weak Acids and Bases and Their Salts", weak acids are relatively common, even in the foods we eat. But we occasionally encounter a strong acid or base, such as stomach acid, which has a strongly acidic pH of 1.7. By definition, strong acids and bases can produce a relatively large amount of H+ or OHions and consequently have marked chemical activities. In addition, very small amounts of strong acids and bases can change the pH of a solution very quickly. If 1 mL of stomach acid [approximated as 0.1 M HCl(aq)] were added to the bloodstream and no correcting mechanism were present, the pH of the blood would decrease from about 7.4 to about 4.7a pH that is not conducive to continued living. Fortunately, the body has a mechanism for minimizing such dramatic pH changes. The mechanism involves a buffer, a solution that resists dramatic changes in pH. Buffers do so by being composed of certain pairs of solutes: either a weak acid plus a salt derived from that weak acid or a weak base plus a salt of that weak base. For example, a buffer can be composed of dissolved HC2H3O2 (a weak acid) and NaC2H3O2 (the salt derived from that weak acid). Another example of a buffer is a solution containing NH3 (a weak base) and NH4Cl (a salt derived from that weak base). Let us use an HC2H3O2/NaC2H3O2 buffer to demonstrate how buffers work. If a strong basea source of OH(aq) ionsis added to the buffer solution, those OH ions will react with the HC2H3O2 in an acid-base reaction:. Choices: - inert - neutral - stable - buffer A:
**Answer**
buffer

*Question*
Q: What is the main difference between prokaryotic or eukaryotic cells ? Read this paragraph and choose the correct option from the provided answers: The answer depends on if the cell is prokaryotic or eukaryotic. The main difference between the two types of cells is the presence of a nucleus. And in eukaryotic cells, DNA lives in the nucleus. Choices: - the type of metabolic waste - the presence of cell walls - the presence of a Golgi Apparatus - the presence of a nucleus A:
**Answer**
the presence of a nucleus

*Question*
Q: Gravitropism ensures that roots grow into the soil and that shoots grow toward what? Read this paragraph and choose the correct option from the provided answers: Plant Responses to Gravity Whether or not they germinate in the light or in total darkness, shoots usually sprout up from the ground, and roots grow downward into the ground. A plant laid on its side in the dark will send shoots upward when given enough time. Gravitropism ensures that roots grow into the soil and that shoots grow toward sunlight. Growth of the shoot apical tip upward is called negative gravitropism, whereas growth of the roots downward is called positive gravitropism. Amyloplasts (also known as statoliths) are specialized plastids that contain starch granules and settle downward in response to gravity. Amyloplasts are found in shoots and in specialized cells of the root cap. When a plant is tilted, the statoliths drop to the new bottom cell wall. A few hours later, the shoot or root will show growth in the new vertical direction. The mechanism that mediates gravitropism is reasonably well understood. When amyloplasts settle to the bottom of the gravity-sensing cells in the root or shoot, they physically contact the endoplasmic reticulum (ER), causing the release of calcium ions from inside the ER. This calcium signaling in the cells causes polar transport of the plant hormone IAA to. Choices: - the north pole - trees - the south pole - sunlight A:
**Answer**
sunlight

*Question*
Q: What is the thick fluid in the space between bones that cushions the joint? Read this paragraph and choose the correct option from the provided answers: Movable joints are also known as synovial joints. This is because the space between the bones is filled with a thick fluid, called synovial fluid, that cushions the joint (see Figure below ). Choices: - interstitial fluid - amniotic fluid - collagen - synovial fluid A:
**Answer**
synovial fluid