1. The amino acid sequence of the respiratory chain carrier molecule cytochrome c is almost identical in all organisms. Disorders caused by abnormal cytochrome c are unknown. What do these two observations suggest about the importance of this molecule?

2. Health food stores sell a product called “pyruvate plus,” which supposedly boosts energy. Why is this product unnecessary?

3. A student regularly runs 3 miles (1.9 kilometers) each afternoon at a slow, leisurely pace. One day, she runs a mile as fast as she can. Afterwards she is winded and feels pain in her chest and leg muscles. She thought she was in great shape! What, in terms of energy metabolism, has she experienced?

4. Two men weigh 230 pounds each. One is 6 feet tall and a bodybuilder, with tight, bulging muscles. The other is 5 feet, 4 inches tall and obese. Which man probably has the higher basal metabolic rate? Why?

Additional Questions and Terms

1. Fructose intolerance is an inherited disorder in which a missing enzyme makes a person unable to use fructose, a simple sugar abundant in fruit. Infants with the condition have very low mental and motor function. Older children are very lethargic and mildly mentally disabled. By adulthood, the nervous system of a person with fructose intolerance deteriorates, eventually causing mental illness and death.

Molecules derived from fructose are intermediates in the first few reactions of glycolysis. The missing enzyme would normally catalyze these reactions. Considering this information about the whole-body and biochemical effects of fructose intolerance, suggest what might be happening on a cellular level to these people.