Question

Which of the following molecules will produce the most ATP per mole?e. 𝛼-ketoglutarate or fumarate in one turn of the citric acid cycle

Accepted Answer

Understand the context of the problem: The citric acid cycle (also known as the Krebs cycle) is a metabolic pathway that generates ATP, NADH, and FADH₂ through the oxidation of acetyl-CoA. The question asks which molecule, 𝛼-ketoglutarate or fumarate, produces the most ATP per mole in one turn of the cycle. Recall the role of each molecule in the citric acid cycle: 𝛼-ketoglutarate is converted to succinyl-CoA via oxidative decarboxylation, producing NADH. Fumarate is formed later in the cycle from succinate and does not directly produce NADH or FADH₂ during its formation. Consider the energy yield of each step: NADH and FADH₂ are electron carriers that contribute to ATP production during oxidative phosphorylation. The conversion of 𝛼-ketoglutarate to succinyl-CoA generates NADH, which can lead to ATP production. Fumarate itself does not directly generate NADH or FADH₂ but is involved in subsequent steps that may produce these carriers. Compare the ATP yield: Since 𝛼-ketoglutarate produces NADH during its conversion to succinyl-CoA, it contributes more to ATP production compared to fumarate, which does not directly produce NADH or FADH₂. Conclude the reasoning: Based on the energy yield of the citric acid cycle, 𝛼-ketoglutarate will produce more ATP per mole than fumarate in one turn of the cycle due to its role in generating NADH.

Which of the following molecules will produce the most ATP per mole?
e. 𝛼-ketoglutarate or fumarate in one turn of the citric acid cycle

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Concetti chiave

Citric Acid Cycle

ATP Yield from Metabolites

Oxidative Phosphorylation