Question 1

What happens to the acetyl groups produced during beta-oxidation of fat?

Accepted Answer

The acetyl groups produced during beta-oxidation of fat are directly fed into the citric acid cycle, where they are oxidized to produce ATP through oxidative phosphorylation. This is the main way that the body generates energy from fat metabolism.

Question 2

Canine phosphofructokinase (PFK)deficiency afflicts Springer spaniels,affecting an estimated 10% of the breed.What is one implication of the genetic defect resulting in PFK deficiency in dogs?

Accepted Answer

Canine PFK deficiency leads to an inability to generate ATP through glycolysis, resulting in inadequate amounts of ATP for energy-intensive activities such as exercise. This leads to exercise intolerance in affected dogs.

Question 3

If you were to add one of the eight citric acid cycle intermediates to the culture medium of yeast growing in the laboratory,what do you think would happen to the rates of ATP and carbon dioxide production?

Accepted Answer

The addition of a citric acid cycle intermediate would likely enhance the activity of the cycle and increase the production of ATP and carbon dioxide. Therefore, the rates of ATP production and carbon dioxide production would both increase.

Question 4

Why is the chemiosmotic hypothesis an important concept in our understanding of cellular metabolism?

Accepted Answer

The chemiosmotic hypothesis explains the mechanism of ATP synthesis through a proton motive force, which is a critical aspect of cellular metabolism.

Question 5

What is the electron transport chain?

Accepted Answer

The electron transport chain is a series of redox reactions where electrons are transferred from electron donors (such as NADH) to electron acceptors (such as oxygen) through a series of membrane-bound electron carriers, resulting in the generation of a proton gradient across the membrane that is used to synthesize ATP.

Question 6

New biosensors,applied like a temporary tattoo to the skin,can alert serious athletes that they are about to "hit the wall" and find it difficult to continue exercising.These biosensors monitor lactate,a form of lactic acid,released in sweat during strenuous exercise.Which of the statements below is the best explanation of why athletes would need to monitor lactate levels?

Accepted Answer

Lactate is produced during anaerobic respiration when muscles cells need more energy. However, when lactate levels increase beyond a certain point, muscle cells eventually fatigue and performance suffers. Therefore, monitoring lactate levels can help athletes modify their activities to increase aerobic respiration and avoid hitting the wall.

Question 7

Which of the following best describes the proton-motive force?

Accepted Answer

The proton-motive force refers to the electrochemical gradient of protons (H+) across the inner mitochondrial membrane, which is generated by the pumping of protons across the membrane during the electron transport chain. As a result, there is a higher concentration of protons in the intermembrane space compared to the mitochondrial matrix. This gradient of protons represents a form of potential energy that can be harnessed to generate ATP through ATP synthase. Thus, option A is the correct answer.

Question 8

Which of the following events takes place in the electron transport chain?

Accepted Answer

The electron transport chain is responsible for extracting energy from high-energy electrons remaining from glycolysis and the citric acid cycle. This energy is then used to create a proton gradient, which powers ATP synthesis through oxidative phosphorylation. The breakdown of glucose into pyruvate occurs during glycolysis, the breakdown of an acetyl group to carbon dioxide occurs during the citric acid cycle, substrate-level phosphorylation involves directly transferring a phosphate group to ADP to form ATP, and reduction of ADP to ATP can occur through various processes, with oxidative phosphorylation being one of them.

Quiz 9: Cellular Respiration and Fermentation