MCAT Biochemistry Question 139: Answer and Explanation
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Question: 139
4. Which of the following processes has the following net reaction?
2 acetyl-CoA + 6 NAD+ + 2 FAD + 2 GDP + 2 Pi + 6 H2O → 4 CO2 + 6 NADH + 2 FADH2 + 2 GTP + 6 H+ + 2 CoA–SH
- A. Glycolysis
- B. Fermentation
- C. Tricarboxylic acid cycle
- D. Electron transport chain
Correct Answer: C
Explanation:
It is not necessary to have all the net reactions memorized for each metabolic process to answer this question; all we need is to identify a few key reactants and products. In this case, we start with acetyl-CoA and end with CoA–SH. We also notice that in this reaction, NAD+ and FAD are reduced to NADH and FADH2, and that CO2 is formed. The only metabolic process in which all of the above reactions would occur is the citric acid cycle, also called the tricarboxylic acid (TCA) or Krebs cycle.