GCSE Biology Practice Exam 2026 – Comprehensive Study Resource

In plants, anaerobic respiration occurs when oxygen is not available for cellular processes. During this type of respiration, glucose is partially broken down to generate energy, and one of the byproducts of this process is ethanol. This is particularly relevant in situations such as fermentation, where yeast (a type of plant) converts sugars into alcohol and carbon dioxide under anaerobic conditions.

While oxygen and water are produced in aerobic respiration, they are not byproducts of anaerobic respiration. Lactic acid is produced in animal cells during anaerobic respiration, but it is not involved in plant respiration. Thus, ethanol is correctly identified as the byproduct of anaerobic respiration in plants.