alleryStart learning →Which statement about the citric acid cycle and oxygen is correct?
AIt consumes oxygen directly at two steps
BIt does not directly consume oxygen at all
CIt releases free oxygen on every turn
DIt replaces oxygen with carbon dioxide
Answer & Solution
Correct answer: B. It does not directly consume oxygen at all
1. The citric acid cycle is still called an aerobic pathway, which invites the wrong conclusion.
2. It is aerobic because its reduced carriers must hand electrons to a later pathway that uses oxygen.
3. The cycle itself does not directly consume oxygen.
4. It also produces very little adenosine triphosphate directly.
5. If the transfer of electrons onward does not happen, the oxidation steps of the cycle stop as well.
6. Free oxygen is a product of photosynthesis, never of this cycle, so that option inverts the chemistry.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.3 Oxidation of Pyruvate and the Citric Acid Cycle_
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