AP BIOLOGY

Detailed explanation-1: -Muscle cells can continue to produce ATP when oxygen runs low using lactic acid fermentation.

Detailed explanation-2: -Lactic acid fermentation is the type of anaerobic respiration carried out by yogurt bacteria (Lactobacillus and others) and by your own muscle cells when you work them hard and fast. Figure 15.3.

Detailed explanation-3: -This is because your muscle cells used lactic acid fermentation for energy. This causes lactic acid to build up in the muscles. It is the buildup of lactic acid that makes the muscles feel tired and sore.

Detailed explanation-4: -Oxygen is then used to break down the unwanted lactic acid into carbon dioxide and water. So, when there is insufficient oxygen to keep up with the production of lactic acid, oxygen debt and muscular fatigue occur.

Detailed explanation-5: -In the absence of oxygen (anaerobic glycolysis), a molecule of glucose is broken down into lactic acid, with the generation of two ATP molecules during the process (Fig. 5.20).