Yeast can respire anaerobically. Describe the process of anaerobic respiration in yeast, including the conditions required, the products formed, and how this process differs from anaerobic respiration in muscle cells.

Anaerobic respiration in yeast occurs in the absence of oxygen.
1. Glucose is metabolised by glycolysis to produce two molecules of pyruvate.
2. Pyruvate is decarboxylated to acetaldehyde and CO₂.
3. Acetaldehyde is reduced by alcohol dehydrogenase to ethanol, regenerating NAD⁺.
The process requires a low‑oxygen environment and produces ethanol and CO₂ as the main products.
In contrast, muscle cells carry out anaerobic respiration (lactic acid fermentation) where pyruvate is converted to lactate by lactate dehydrogenase, not to ethanol and CO₂. Both pathways yield less ATP per glucose than aerobic respiration, making them less efficient.