Fermentation — practice questions

Question 1 · difficulty L1 · recall

Which end products are formed during alcoholic fermentation in yeast?

• A. Lactate and carbon dioxide
• B. Ethanol and carbon dioxide
• C. Acetyl-CoA and oxygen
• D. Pyruvate and water

Question 2 · difficulty L2 · understanding

What is the main metabolic purpose of fermentation after glycolysis?

• A. To oxidise acetyl-CoA in the Krebs cycle
• B. To generate large amounts of ATP in mitochondria
• C. To regenerate NAD+ from NADH
• D. To split oxygen into reactive atoms

Question 3 · difficulty L3 · understanding

What amount of energy is released from glucose during lactic acid fermentation?

• A. Approximately 15%
• B. More than 18%
• C. About 10%
• D. Less than 7%

Question 4 · difficulty L3 · application

Muscle cells temporarily rely more on lactic acid fermentation when oxygen delivery cannot meet demand. What immediate advantage does this provide?

• A. It prevents glucose from entering glycolysis
• B. It increases the ATP yield of the Krebs cycle
• C. It converts lactate directly into oxygen
• D. It restores NAD+ needed for glycolysis

Question 5 · difficulty L4 · analysis

Yeast cells are supplied with abundant glucose but no oxygen. They continue producing ATP at a low rate and release carbon dioxide. Which process best explains both observations?

• A. Glycolysis coupled to alcoholic fermentation
• B. Krebs cycle coupled to oxidative phosphorylation
• C. Only the electron transport chain
• D. Photorespiration

Question 6 · difficulty L5 · analysis

A mutant yeast strain performs glycolysis normally but cannot convert acetaldehyde to ethanol. Under anaerobic conditions, which problem will most directly stop sustained ATP production?

• A. Glucose cannot be phosphorylated
• B. NADH will not be efficiently reoxidised to NAD+
• C. Pyruvate cannot be formed
• D. ATP synthase will make excess ATP