What is the final electron acceptor in lactic acid fermentation? NADH acetaldehyde pyruvic acid lactic acid
The Correct Answer and Explanation is:
The correct answer is: pyruvic acid.
Explanation
Lactic acid fermentation is an anaerobic metabolic process used by certain cells to generate energy when oxygen is not available. In this process, pyruvic acid acts as the final electron acceptor.
During glycolysis, one molecule of glucose is broken down into two molecules of pyruvic acid. This process produces a small amount of ATP (adenosine triphosphate) and reduces NAD+ to NADH. However, in the absence of oxygen, the cell cannot use the electron transport chain to regenerate NAD+ from NADH. Without NAD+, glycolysis would stop, and energy production would cease.
To solve this problem, cells performing lactic acid fermentation use pyruvic acid as an internal electron acceptor. NADH donates its electrons to pyruvic acid, reducing it to lactic acid. This reaction is catalyzed by the enzyme lactate dehydrogenase. The chemical equation for this step is:
Pyruvic acid + NADH → Lactic acid + NAD+
The key purpose of this step is to regenerate NAD+, which is essential to keep glycolysis going. By continuously converting pyruvic acid into lactic acid, the cell ensures a steady supply of NAD+ for glycolysis to proceed, allowing ATP production to continue even when oxygen is not available.
This type of fermentation occurs in certain bacteria, like Lactobacillus, and in human muscle cells during intense exercise when oxygen levels are low. The accumulation of lactic acid in muscle cells can lead to temporary fatigue and soreness.
To summarize, pyruvic acid is the final electron acceptor in lactic acid fermentation, accepting electrons from NADH to form lactic acid. This allows cells to maintain energy production under anaerobic conditions by sustaining glycolysis through the regeneration of NAD+.
