Question

If you were to expose cells that are undergoing aerobic respiration to a radioactive carbon isotope in the form of C6H12O6, which of the following molecules would you not expect to be radiolabeled?

(a) pyruvate
(b) NADH
(c) water
(d) CO2

Answer 1

Answer:

The correct answer is option (c) "water".

Explanation:

Cells that are undergoing aerobic respiration and are exposed to a radioactive carbon isotope in the form of C6H12O6 will have radiolabeled its molecules that are involved in aerobic respiration and contain carbon. In this case, the only molecule that does not contain carbon in the options is water, therefore water will not be radiolabeled. Water is comprised of two atoms of hydrogen and one atom of oxygen, while pyruvate, NADH and CO2 all contain carbon.