Which of the following is LEAST likely to occur in a muscle fiber that is metabolizing anaerobically?

Which of the following is LEAST likely to occur in a muscle fiber that is metabolizing anaerobically?

• A. Fermentation of glucose to lactic acid
• B. Phosphorylation of ADP within the electron transport chain
• C. Depletion of stores of glycogen
• D. Acidification of the cytoplasm

Answer: (B)

The process of anaerobic metabolism in muscle fibers primarily occurs when oxygen is scarce, particularly during intense exercise. In this condition, muscle cells rely on anaerobic glycolysis to generate ATP quickly from glucose. The end product of this anaerobic pathway is lactic acid, which results from the fermentation of glucose. As a consequence of consistently operating in this manner, the muscle fibers experience several changes. Phosphorylation of ADP within the electron transport chain is an aerobic process that requires oxygen. This pathway occurs in the mitochondria and relies on the presence of oxygen to facilitate the transfer of electrons and produce ATP. Since anaerobic metabolism lacks oxygen, the electron transport chain does not function effectively, making phosphorylation of ADP within that pathway unlikely in a muscle fiber that is solely relying on anaerobic processes. In contrast, anaerobic metabolism leads to the fermentation of glucose into lactic acid, results in the depletion of glycogen stores due to the consumption of glucose, and causes an accumulation of lactic acid in the cytoplasm, which lowers the pH and acidifies it. These conditions are characteristic of anaerobic glycolysis and reflect the metabolic shifts that occur when muscle fibers are functioning without adequate oxygen supply. Thus, it is clear why phosphorylation of AD

The process of anaerobic metabolism in muscle fibers primarily occurs when oxygen is scarce, particularly during intense exercise. In this condition, muscle cells rely on anaerobic glycolysis to generate ATP quickly from glucose. The end product of this anaerobic pathway is lactic acid, which results from the fermentation of glucose. As a consequence of consistently operating in this manner, the muscle fibers experience several changes.

Phosphorylation of ADP within the electron transport chain is an aerobic process that requires oxygen. This pathway occurs in the mitochondria and relies on the presence of oxygen to facilitate the transfer of electrons and produce ATP. Since anaerobic metabolism lacks oxygen, the electron transport chain does not function effectively, making phosphorylation of ADP within that pathway unlikely in a muscle fiber that is solely relying on anaerobic processes.

In contrast, anaerobic metabolism leads to the fermentation of glucose into lactic acid, results in the depletion of glycogen stores due to the consumption of glucose, and causes an accumulation of lactic acid in the cytoplasm, which lowers the pH and acidifies it. These conditions are characteristic of anaerobic glycolysis and reflect the metabolic shifts that occur when muscle fibers are functioning without adequate oxygen supply. Thus, it is clear why phosphorylation of AD