What are the roles of the three stages of cellular respiration?

The three stages of cellular respiration are primarily glycolysis, the Krebs cycle (also known as the citric acid cycle), and oxidative phosphorylation. In this process, glycolysis serves as the first step, where glucose is broken down into pyruvate, generating a small amount of ATP and two molecules of NADH, which are important electron carriers.

The second stage, the Krebs cycle, occurs in the mitochondria. Here, the pyruvate produced from glycolysis is further broken down, releasing carbon dioxide and generating more electron carriers in the form of NADH and FADH2, as well as a small amount of ATP. These carriers are vital for the next stage because they transport high-energy electrons to the electron transport chain.

In the final stage, oxidative phosphorylation, the electron transport chain uses electrons from NADH and FADH2 to generate a proton gradient across the mitochondrial membrane. This gradient is then used to produce a large amount of ATP via ATP synthase. Ultimately, oxidative phosphorylation is where the bulk of ATP is synthesized during cellular respiration.

This understanding highlights the unique contributions of each stage: glycolysis initiates glucose breakdown, the Krebs cycle provides important electron carriers, and oxidative phosphorylation is responsible for the majority of ATP production.