Question 1

Several students were talking about which came first in the history of the Earth.Which student has the best understanding of what happened?

Accepted Answer

Anaerobic organisms likely came first because early Earth's atmosphere lacked oxygen, and these organisms do not require oxygen to survive.

Question 2

Electron transport takes place in the ________.

Accepted Answer

Electron transport occurs primarily in the inner mitochondrial membrane through a series of protein complexes known as the electron transport chain.

Question 3

A product of glycolysis is ________.

Accepted Answer

The product of glycolysis is pyruvic acid, which can then be converted into either lactic acid or ethanol in certain organisms depending on whether the organism is using aerobic or anaerobic respiration. O₂ is not a direct product of glycolysis.

Question 4

The second stage of aerobic respiration is ________.

Accepted Answer

The citric acid cycle, also known as the Krebs cycle, is the second stage of aerobic respiration. It occurs in the mitochondria and involves the oxidation of acetyl-CoA to produce ATP, NADH, and FADH2.

Question 5

Some friends are trying to make wine in their basement.They've added yeast to a sweet grape juice mixture and have allowed the yeast to grow.After several days,they find that sugar levels in the grape juice have dropped,but there's no alcohol in the mixture.The most likely explanation is that ________.

Accepted Answer

Yeast only produces alcohol in the absence of oxygen, so if there is no alcohol in the mixture, it is likely that there is too much oxygen present. This can be corrected by reducing the oxygen availability, which can be done by sealing the container and using an airlock to prevent oxygen from entering while still allowing carbon dioxide to escape.

Question 6

In Texas,a man showed up at a medical facility claiming that he felt drunk when he had not ingested any alcohol.Indeed his blood alcohol measured 0.37,many times the legal limit.Although he was a home brewer,he claimed that this intoxication had been happening often without his drinking any alcohol.Which of these hypotheses and actions might be most useful in diagnosing this problem?

Accepted Answer

This hypothesis is related to a potential overgrowth of yeast in the gut, which can cause the body to produce alcohol from the fermentation of carbohydrates. Taking probiotics and a low carb diet can help rebalance gut bacteria and potentially resolve the issue. This is supported by research that shows a correlation between gut microbiota and blood alcohol levels. The other options do not provide as strong of a link to the presented symptoms.

Question 7

A child is born with a rare disease in which mitochondria are missing from certain skeletal muscle cells.Physicians find that the muscle cells function.Not surprisingly,they also find that ________.

Accepted Answer

The absence of mitochondria in certain muscle cells means that these cells cannot undergo oxidative phosphorylation, the process by which mitochondria generate ATP from glucose and oxygen. Instead, they rely on anaerobic glycolysis to generate ATP. This process produces lactic acid as a byproduct, which can accumulate in the muscles following exercise. Therefore, option A is the best choice. Options B and C are incorrect because carbon dioxide and oxygen are not directly related to the absence of mitochondria in the muscle cells. Option D is incorrect because muscle cells can still undergo glycolysis, even in the absence of mitochondria.

Question 8

Large amounts of oxygen gas first appeared in Earth's atmosphere about ________ years ago.

Accepted Answer

Large amounts of oxygen gas first appeared in Earth's atmosphere about 2.7 billion years ago during the Great Oxidation Event, when photosynthetic organisms began producing oxygen.

Question 9

In cellular respiration,most ATP is produced DIRECTLY as a result of ________.

Accepted Answer

The movement of hydrogen ions across the inner mitochondrial membrane, also known as chemiosmosis, drives ATP synthesis by ATP synthase, producing most of the ATP in cellular respiration.

Question 10

What waste product do yeast produce under anaerobic conditions?

Accepted Answer

Yeast produce ethyl alcohol as a waste product under anaerobic conditions through the process of fermentation. Pyruvic acid and lactic acid are also waste products, but they are produced by different types of microorganisms under different conditions. Creatine is not a waste product produced by microorganisms, but rather a substance found in muscle tissue.

Question 11

Which part of cellular respiration produces the most NADH?

Accepted Answer

The citric acid cycle, also known as the Krebs cycle, produces the most NADH out of all the stages of cellular respiration. During the citric acid cycle, NAD+ is reduced to NADH by accepting electrons and hydrogen ions from the breakdown of acetyl CoA. Two molecules of NADH are produced for every turn of the cycle, which occurs twice per glucose molecule that enters cellular respiration.

Question 12

Human muscle cells use lactic acid fermentation to ________.

Accepted Answer

Human muscle cells use lactic acid fermentation to produce ATP without O₂, as they cannot rely on aerobic respiration during short bursts of activity or in the absence of adequate oxygen supply. Lactic acid fermentation allows for the regeneration of NAD+ from NADH, which can then be used in glycolysis to produce more ATP. However, this process is not as efficient as aerobic respiration and can lead to a buildup of lactic acid, which can cause muscle fatigue and soreness.

Question 13

Which of the following metabolic pathways is common to both aerobic and anaerobic processes of sugar breakdown?

Accepted Answer

Glycolysis is the common metabolic pathway to both aerobic and anaerobic processes of sugar breakdown. It occurs in the cytoplasm of all types of cells and produces two molecules of pyruvate, ATP, and NADH. The pyruvate enters either the citric acid cycle in aerobic respiration or conversion to lactic acid in anaerobic respiration. The electron transport chain occurs only in aerobic respiration, where NADH is oxidized to produce ATP.

Question 14

ATP synthase plays a role in ________.

Accepted Answer

The answer of ATP synthase plays a role in ________.
...

Question 15

Which of these stages of cell respiration can occur without the others?

Accepted Answer

Glycolysis can occur independently of the other stages as it does not require oxygen and takes place in the cytoplasm, unlike the other processes that require mitochondria and oxygen.

Question 16

Aerobic cellular respiration generates about ________ ATP from one glucose.

Accepted Answer

Aerobic cellular respiration generates approximately 38 ATP from one glucose molecule. This process involves three major stages: glycolysis, the Krebs cycle, and the electron transport chain. During glycolysis, two ATP molecules are generated, while the Krebs cycle yields two ATP, eight NADH, and two FADH2 molecules. These electron carriers are then used during the electron transport chain to generate a maximum of 34 ATP molecules. Therefore, in total, 38 ATP molecules can be produced through aerobic respiration.

Question 17

What must pyruvic acid be converted to before it can enter the citric acid cycle?

Accepted Answer

Pyruvic acid must be converted to acetyl CoA before it can enter the citric acid cycle. This conversion occurs via the enzyme pyruvate dehydrogenase and involves the removal of a carbon dioxide molecule and the transfer of electrons to NAD+ to form NADH. The resulting acetyl CoA molecule can then enter the citric acid cycle in the mitochondria.

Question 18

In aerobic respiration,how many molecules of acetic acid are produced from six molecules of glucose?

Accepted Answer

In aerobic respiration, each molecule of glucose is converted into two molecules of pyruvate, which are then converted into two molecules of acetic acid (acetyl-CoA). Therefore, six molecules of glucose produce 12 molecules of acetic acid.

Question 19

Which of the following is a result of glycolysis?

Accepted Answer

Glycolysis is the process of breaking down glucose into pyruvic acid, which is the first step in cellular respiration that occurs in the cytoplasm of cells. This process results in the production of a net gain of two ATP molecules per glucose molecule and the conversion of NAD⁺ to NADH. It does not produce CO₂.

Question 20

Anaerobic respiration produces a maximum of ________ ATP per glucose.

Accepted Answer

Anaerobic respiration, also known as fermentation, produces a maximum of 2 ATP per glucose molecule. This is because it does not involve the electron transport chain that produces the majority of ATP in aerobic respiration. Instead, fermentation relies on glycolysis, which produces a net of 2 ATP molecules.

Quiz 6: Cellular Respiration: Obtaining Energy From Food