Chapter 8

Explain how the reactions that produce and use ATP serve, together, as an energy shuttle mechanism in cells.

Explain the concept of redox balance. What conditions must exist, for example, for cytochrome oxidase to be in redox balance?

How does the reduction of pyruvic acid create a state of redox balance in anaerobic glycolysis?

Outline the chemiosmotic hypothesis for the mechanism by which oxidative phosphorylation is coupled with electron transport. How does uncoupling occur in tissues with uncoupling protein 1 (UCP1)? Under what circumstances would uncoupling be disadvantageous, and under what circumstances might it be advantageous?

Using two or three carefully chosen examples, illustrate the point that during physical activity, behavior and biochemistry are intimately linked, such that an animal's exercise performance depends on the mechanisms that are making ATP for the exercise.

Assuming that an animal uses a catabolic pathway that produces organic products, such as lactic acid or propionic acid, compare the pros and cons of retaining or excreting the organic molecules.

Why is it important to distinguish temporary electron (hydrogen) acceptors in cells from final electron acceptors? What are the unique advantages of \(\mathrm{O}_{2}\) as an electron acceptor?

Why does an oxygen deficit occur at the start of submaximal exercise in vertebrates? What are the mechanisms of ATP production during the oxygen deficit phase, and how is ATP made in the ensuing pay-as-you-go phase?

A single individual can differ from time to time in his or her maximal rate of \(\mathrm{O}_{2}\) consumption. For example, athletic training in people can raise the maximal rate of \(\mathrm{O}_{2}\) consumption by \(10-30 \%\), whereas going to high altitudes can lower it (see Box 8.3). Explain how these sorts of changes in the maximal rate of \(\mathrm{O}_{2}\) consumption can make a single type of exercise (such as jogging at 6 miles per hour) shift from being submaximal to supramaximal, or vice versa. What are the physiological implications of such shifts?

There has been a great deal of debate over whether the ratio of \(\mathrm{SO}\) to FG fibers in the muscles of individual people or other animals is fixed genetically. Researchers have asked whether the ratio of fiber types can be altered during an individual's lifetime by various sorts of training or other experiences. Why would a change in the ratio of fiber types be of interest and importance? Design experiments or other sorts of studies that would help elucidate whether the ratio of fiber types can undergo change.