How can yeast cells grow on glycerol despite mutations in glycolysis?

How can yeast cells grow on glycerol despite mutations in glycolysis?

• A. Glycerol can feed into the citric acid cycle and generate ATP via electron transport and chemiosmosis.
• B. Glycerol is converted back to glucose via gluconeogenesis.
• C. Glycerol directly produces ATP in glycolysis.
• D. Glycerol bypasses mitochondria.

Answer: (A)

The ability to use glycerol for growth relies on metabolic flexibility—glycerol can be converted into central carbon intermediates that feed directly into the citric acid cycle and then into the electron transport chain for ATP production. Glycerol is first turned into glycerol-3-phosphate and then into a form of dihydroxyacetone phosphate. From there, the carbon can be funneled toward acetyl-CoA and into the citric acid cycle. As the cycle runs, NADH and FADH2 feed the electron transport chain, driving ATP synthesis by chemiosmosis. Even if steps in glycolysis are impaired, respiration can still proceed using these acetyl-CoA–derived inputs, providing energy for growth. Gluconeogenesis wouldn’t primarily support rapid growth on glycerol because turning glycerol into glucose is energy-intensive and not the main energy source in this scenario. Glycerol does not directly produce ATP by glycolysis, and the idea that glycerol would bypass mitochondria ignores the main pathway for efficient ATP production from glycerol-derived carbon. While some organisms can manage without mitochondria in certain conditions, growth on glycerol as described relies on mitochondrial ATP production through the citric acid cycle and oxidative phosphorylation.

The ability to use glycerol for growth relies on metabolic flexibility—glycerol can be converted into central carbon intermediates that feed directly into the citric acid cycle and then into the electron transport chain for ATP production. Glycerol is first turned into glycerol-3-phosphate and then into a form of dihydroxyacetone phosphate. From there, the carbon can be funneled toward acetyl-CoA and into the citric acid cycle. As the cycle runs, NADH and FADH2 feed the electron transport chain, driving ATP synthesis by chemiosmosis. Even if steps in glycolysis are impaired, respiration can still proceed using these acetyl-CoA–derived inputs, providing energy for growth.

Gluconeogenesis wouldn’t primarily support rapid growth on glycerol because turning glycerol into glucose is energy-intensive and not the main energy source in this scenario. Glycerol does not directly produce ATP by glycolysis, and the idea that glycerol would bypass mitochondria ignores the main pathway for efficient ATP production from glycerol-derived carbon. While some organisms can manage without mitochondria in certain conditions, growth on glycerol as described relies on mitochondrial ATP production through the citric acid cycle and oxidative phosphorylation.