Question

The citric acid cycle is a series of oxidation reactions that removes carbon atoms

from substrates in the form of CO2. Where do the oxygen atoms in the carbon
dioxide molecules come from?______
(a) water
(b) phosphates
(c) molecular oxygen
(d) acetyl CoA

Answer 1

The oxygen atoms in the carbon dioxide molecules produced during the citric acid cycle come from water, not molecular oxygen, phosphates, or acetyl CoA.

Step-by-step explanation:

The oxygen atoms in the carbon dioxide (CO2) molecules produced during the citric acid cycle come from water molecules.

This occurs because as substrates are oxidized, high-energy electrons are removed and transferred to carriers such as NADH and FADH2.

These electrons are eventually used in the electron transport chain, which consumes oxygen and produces water, indirectly providing the oxygen for CO2 production. The correct answer to the question is (a) water.