Question

You continue this approach by designing two separate experiments. In the first experiment, you use glucose where "Coccupies position 1. In the second experiments, 14C occupies position 2 and 6 in the glucose molecules. For each experiment, you use 0.2 moles of radiolabeled glucose and you assume that all the pyruvate formed is converted to acetyl-CoA. What following statements are correct? (select 3)
a) When glucose is labeled on carbon #1, 0.2 mole of acetyl-CoA is radiolabeled
b) When glucose is labeled on carbon #1, 0.1 mole of acetyl-CoA is radiolabeled
c) When glucose is labeled on carbons #2 and #6, 0.2 mole of acetyl-CoA is radiolabeled
d) When glucose is labeled on carbons #2 and 6, 0.1 mole of acetyl-CoA is radiolabeled
e) When glucose is labeled on carbons #2 and 6, the carbonyl groups of half of the acetyl-CoA molecules are radiolabeled
f) When glucose is labeled on carbons #2 and 6, the methyl groups of half of the acetyl-CoA molecules are radiolabeled

Answer 1

Answer:

b) When glucose is labeled on carbon #1, 0.1 mole of acetyl-CoA is radiolabeled

c) When glucose is labeled on carbons #2 and #6, 0.2 mole of acetyl-CoA is radiolabeled

e) When glucose is labeled on carbons #2 and 6, the carbonyl groups of half of the acetyl-CoA molecules are radiolabeled

f) When glucose is labeled on carbons #2 and 6, the methyl groups of half of the acetyl-CoA molecules are radiolabeled

Explanation:

When glucose undergoes glycolysis, it is converted into two molecules of pyruvate with carbon 1 to 3 forming the first molecule of pyruvate and carbon 4 to 6 the second molecule of pyruvate. The C-1 and C-6 of the glucose molecule becomes the methyl groups of each of the two molecules of pyruvate. The C-2 and C-5  of the glucose molecule forms the carbonyl carbon of each of the two pyruvate molecules. Each of the two pyruvate molecules undergoes further oxidation to yield acetyl-CoA with the carbonyl and methyl groups of pyruvate retained in the acetyl-CoA molecules.

Thus when 0.2 moles of glucose are labelled at C-1 and then C-2 and C-6 in each of the two experiments the following results are obtained:

When glucose is labeled on carbon-1, 0.1 mole of acetyl-CoA is radiolabeled  since half of the two pyruvate molecules are obtained from C-1

When glucose is labeled on carbon-2 and carbon-6, 0.2 mole of acetyl-CoA is radiolabeled since the C-2 and C-6 of the glucose molecules forms a part of one of each of the two pyruvate molecules.

When glucose is labeled on carbons #2 and 6, the carbonyl groups of half of the acetyl-CoA molecules are radiolabeled since one of the two carbonyl groups of the two pyruvate molecules is  formed from C-2 of glucose.

When glucose is labeled on carbon-2 and carbon-6, the methyl groups of half of the acetyl-CoA molecules are radiolabeled since one of the two methyl groups of the two pyruvate molecules is  formed from C-6 of glucose.