Fermentation Transitional Reasoning Download PDF

Questions

1. 1.

   Researchers placed yeast cells into a sealed, oxygen-free flask containing a glucose solution and monitored metabolite levels over time. When a chemical that selectively inhibits alcohol dehydrogenase was added to the culture, the rate of glucose consumption and ATP production dropped to near zero within minutes, despite an abundant supply of glucose and ADP. Which of the following explains why glycolysis ceases under these conditions?

   • A) The inhibition of alcohol dehydrogenase directly halts the synthesis of acetyl-CoA needed for the citric acid cycle.
   • B) Pyruvate molecules can no longer be transported across the mitochondrial membrane without active alcohol dehydrogenase.
   • C) The cell cannot regenerate NAD+ from NADH, which depletes the electron acceptors required for the oxidation of glyceraldehyde-3-phosphate in glycolysis.
   • D) The accumulation of acetaldehyde reverses the substrate-level phosphorylation steps in the energy payoff phase of glycolysis.