What process occurs when the cell undergoes anaerobic respiration?

When a cell undergoes anaerobic respiration, the process it engages in is fermentation. This pathway allows cells to produce energy in the absence of oxygen by converting glucose into acids, gases, or alcohol, depending on the type of fermentation occurring. For example, in alcoholic fermentation, yeast converts glucose into ethanol and carbon dioxide, while in lactic acid fermentation, certain bacteria and animal cells convert glucose into lactic acid.

Glycolysis, while essential for both aerobic and anaerobic respiration, is not exclusively anaerobic; it can occur regardless of the presence of oxygen. The Krebs Cycle and oxidative phosphorylation are primarily aerobic processes that require oxygen and happen after glycolysis if oxygen is present. Therefore, fermentation stands out as the key process that allows cells to derive energy without relying on oxygen, making it the correct answer in this context.