Respiration ❮ 69Lactic acid fermentation (Figure 7.6) occurs in human and animal muscle cells when
oxygen is not available. This is a simpler process than alcoholic fermentation—the pyruvate
is directly reduced to lactate (also known as lactic acid) by NADH to regenerate the NAD+
needed for the resumption of glycolysis. Have you ever had a cramp during exercise? The
pain you felt was the result of lactic acid fermentation. Your muscle was deprived of the
necessary amount of oxygen to continue glycolysis, and it switched over to fermentation.
The pain from the cramp came from the acidity in the muscle.
Figure 7.6 Lactic acid fermentation.http://www.ebook3000.com