Question

In the absence of O2, cells capable of fermentation _______ . Seleccione una: a. can oxidize FAD. b. no longer produce ATP. c. can oxidize NADH to produce NAD+. d. accumulate pyruvate. e. accumulate glucose.

Answer 1

Cells capable of fermentation can oxidize NADH to produce NAD+ in the absence of oxygen, allowing glycolysis to continue and the cell to produce a small amount of ATP. Lactic acid fermentation is an example of this process and is essential for survival in low-oxygen conditions.

Step-by-step explanation:

In the absence of O2, cells capable of fermentation can oxidize NADH to produce NAD+ (option c). This process is crucial for allowing glycolysis to continue, which is the cell's only way of producing ATP in the absence of oxygen. Fermentation essentially recycles electron carriers; without it, a cell would not be able to continue metabolizing glucose through glycolysis, resulting in the death of the cell.

During lactic acid fermentation, for example, pyruvate from glycolysis is reduced directly to lactate, which permits the recycling of NADH back into NAD+. Although this process does not produce as much ATP as aerobic respiration (only two ATP molecules per glucose molecule), it is vital for the survival of cells when oxygen is not available, such as in muscle cells during intense exercise.

It should be noted that fermentation is not just a biological curiosity but has practical applications in the production of foods such as yogurt and beverages like beer, through the use of lactic acid and alcoholic fermentation pathways, respectively.