Question

If skeletal muscles work to the point of fatigue, the muscle cells may not have sufficient oxygen to carry out aerobic respiration. What processes do muscle cells use if oxygen is not available for aerobic respiration?a. lactic acid fermentation b. citric acid cycle c. ethanol fermentation d. glycolysis

Answer 1

Answer:

a. lactic acid fermentation

Explanation:

Under conditions of intense exercise, the oxygen gas obtained by pulmonary respiration may be insufficient to meet the needs of muscle cells in the work of obtaining energy from cellular respiration.

However, even in the absence of oxygen gas, our muscle cells can release the available energy in glucose, leading to even smaller amounts of ATP molecules. Under these conditions, muscle cells perform lactic fermentation, a process that is virtually identical to glycolysis (the first set of cellular respiration reactions), except that pyruvic acid is transformed into lactic acid with the formation of 2 ATPs.  Despite the lower energy yield, fermentation ensures the energy supply to the muscle. Lactic acid formed under these conditions has been associated with muscle pain and fatigue characteristic of intense physical exercise. Recent research, however, has shown that pain is caused by muscle fiber micro-injuries rather than lactic acid as it is rapidly metabolized and eliminated.