Question

For each molecule of glucose that enters glycolysis, _______ acetyl-CoA enter the citric acid cycle.

4

1

2

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5

Answer 1

The correct option is C) 2. Two acetyl-CoA molecules enter the citric acid cycle per one molecule of glucose that undergoes glycolysis, as each glucose is broken down into two pyruvates, which are then converted into acetyl-CoA. These enter the citric acid cycle and contribute to ATP production.

Step-by-step explanation:

For each molecule of glucose that enters glycolysis, two acetyl-CoA enter the citric acid cycle. This is because each glucose molecule is broken down into two molecules of pyruvate during glycolysis, and each pyruvate is then converted into one acetyl-CoA. Hence, the glycolysis of one glucose molecule yields two acetyl-CoA molecules that will each enter the citric acid cycle.

In the presence of oxygen, these acetyl-CoA units combine with a four-carbon molecule, oxaloacetate, to form a six-carbon molecule called citrate or citric acid, each turn of the citric acid cycle processing one acetyl-CoA. This cycle plays a key role in cellular respiration, eventually leading to the production of ATP. As the cycle turns twice per molecule of glucose, it generates a series of products including carbon dioxide, NADH, FADH2, and ATP or GTP.