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: The citric acid cycle (also known as the Krebs cycle) is a central metabolic pathway that generates energy in the form of ATP, NADH, and FADH₂. Each intermediate in the cycle contributes differently to the production of ATP. Identify the molecules in question: α-ketoglutarate and fumarate are intermediates in the citric acid cycle. α-ketoglutarate is converted to succinyl-CoA, while fumarate is converted to malate in subsequent steps of the cycle. Analyze the energy yield of each molecule: The conversion of α-ketoglutarate to succinyl-CoA produces one molecule of NADH. NADH is later used in the electron transport chain to generate approximately 2.5 ATP. Additionally, the conversion of succinyl-CoA to succinate generates one molecule of GTP (equivalent to 1 ATP). Compare this to fumarate: The conversion of fumarate to malate does not directly produce NADH, FADH₂, or ATP. However, the subsequent conversion of malate to oxaloacetate produces one molecule of NADH, which generates approximately 2.5 ATP in the electron transport chain. Conclude: Since α-ketoglutarate produces both NADH and GTP (equivalent to ATP) in its conversion to succinyl-CoA and succinate, it yields more ATP per mole compared to fumarate, which only indirectly contributes to ATP production through NADH formation in a later step.

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