ATP yield and efficiency Transitional Reasoning Practice

Questions

1. 1.

   In eukaryotic cells, the theoretical maximum yield of 36 to 38 ATP per glucose molecule is rarely achieved in vivo, with actual experimental measurements typically ranging between 30 and 32 ATP. Researchers analyzing isolated, intact mitochondria observed that the proton-motive force generated by electron transport is partially expended on supporting cellular transport processes and dissipating as heat. Based on principles of cellular bioenergetics, which biological factor directly contributes to this observed reduction in net ATP yield?

   • A) Complete cessation of the citric acid cycle caused by allosteric feedback inhibition of pyruvate dehydrogenase by elevated cytosolic ADP levels.
   • B) Diversion of cytosolic NADH into lactate production prior to delivering high-energy electrons to the mitochondrial respiratory complexes.
   • C) Consumption of the proton-motive force for the active import of pyruvate and inorganic phosphate into the matrix, along with passive proton leakage across the inner membrane.
   • D) Complete loss of standard free energy because complex II pumps more protons across the inner membrane than complex I.

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