Optimal conditions for yeast anaerobic respiration

Steps:

• Anaerobic respiration in yeast ferments sugar to produce CO2, requiring no oxygen.
• Yeast enzymes work best at 40°C, not higher temperatures that denature proteins.
• Adding oil creates an anaerobic environment by blocking oxygen diffusion.
• Without oil, oxygen allows aerobic respiration, reducing CO2 from fermentation.

Why A is correct:

• Oil ensures anaerobic conditions while 40°C optimizes yeast fermentation of sugar to CO2, as per the equation: C6H12O6 → 2C2H5OH + 2CO2.

Why the others are wrong:

• B: 100°C denatures yeast enzymes, stopping respiration.
• C: No oil permits oxygen entry, favoring aerobic respiration over CO2-producing fermentation.
• D: No oil allows oxygen, and 100°C kills yeast, preventing any respiration.

Final answer: A