Question

Glycogen serves as the primary fuel for ATP production/re-synthesis...

Select one:

a. during short-duration, high-intensity exercise.

b. during severe caloric restriction.

c. after many hours of low-intensity exercise.

d. during periods of starvation.

Answer 1

Answer;

a. during short-duration, high-intensity exercise.

Explanation: Creatine Phosphate: Once the cytosolic stores of ATP are depleted, the cell calls upon another rapid energy source, Creatine Phosphate. Creatine phosphate is a high energy compound that can rapidly transfer its phosphate to a molecule of ADP to quickly replenish ATP without the use of oxygen. This transfer requires the enzyme creatine kinase, an enzyme that is located on the M-line of the sarcomere. Creatine phosphate can replenish the ATP pool several times, enough to extend muscle contraction up to about 10 seconds. Creatine Phosphate is the most widely used supplement by weight lifters.

Glycolysis: Glycolysis, as the name implies, is the breakdown of glucose. The primary source of glucose for this process is from glycogen that is stored in the muscle. Glycolysis can function in the absence of oxygen and as such, is the major source of ATP production during anaerobic activity. This series of chemical reactions will be a major focus in the next unit. Although glycolysis is very quick and can supply energy for intensive muscular activity, it can only be sustained for about a minute before the muscles begin to fatigue.

Aerobic or Oxidative Respiration: The mechanisms listed above can supply ATP for maybe a little over a minute before fatigue sets in. Obviously, we engage in muscle activity that lasts much longer than a minute (things like walking or jogging or riding a bicycle). These activities require a constant supply of ATP. When continuous supplies of ATP are required, the cells employ metabolic mechanisms housed in the mitochondria that utilize oxygen. We normally refer to these processes as aerobic metabolism or oxidative metabolism. Using these aerobic processes, the mitochondria can supply sufficient ATP to power the muscle cells for hours. The down side of aerobic metabolism is that it is slower than anaerobic mechanisms and is not fast enough for intense activity.