In which stages of cellular respiration do aerobic processes occur?

Aerobic processes in cellular respiration primarily occur in the latter stages, specifically from the citric acid cycle (also known as the Krebs cycle) through the electron transport chain, which encompass stages 2 to 4.

In the first stage, glycolysis, the process is anaerobic, meaning it does not require oxygen and occurs in the cytoplasm. However, once glycolysis has converted glucose into pyruvate, if oxygen is present, the pyruvate enters the mitochondria, marking the beginning of the aerobic processes.

In the second stage, pyruvate oxidation leads into the citric acid cycle, which takes place in the mitochondrial matrix. This cycle processes acetyl-CoA generated from pyruvate and produces electron carriers, which are further utilized in the following stage. The third stage is where the electron transport chain operates, which is the primary site for aerobic respiration since it relies on oxygen to accept electrons at the end of the chain, ultimately producing water and generating ATP.

Therefore, stages 2 through 4 are categorized as aerobic processes, leveraging oxygen to maximize energy extraction from glucose, making D the comprehensive choice that encapsulates where aerobic respiration occurs.