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Multiple Choice
Which one of the following substances is a part of both phases A and C of the citric acid cycle?
A
Succinyl CoA
B
Oxaloacetate
C
Acetyl CoA
D
Citrate
Verified step by step guidance
1
Understand the citric acid cycle: The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins into carbon dioxide.
Identify the phases of the citric acid cycle: Phase A involves the combination of Acetyl CoA with Oxaloacetate to form Citrate. Phase C involves the regeneration of Oxaloacetate from Malate.
Recognize the role of Oxaloacetate: Oxaloacetate is a key intermediate in the citric acid cycle. It is involved in the initial step where it combines with Acetyl CoA to form Citrate, and it is regenerated in the final step of the cycle.
Analyze the options: Succinyl CoA is involved in the conversion of succinate to fumarate, Acetyl CoA is the starting molecule that combines with Oxaloacetate, and Citrate is formed from the combination of Acetyl CoA and Oxaloacetate.
Conclude which substance is part of both phases A and C: Oxaloacetate is involved in both the beginning and end of the citric acid cycle, making it a part of both phases A and C.