How is energy released during cellular respiration?

Energy is released during cellular respiration primarily by the breakdown of glucose, a process that involves various metabolic pathways including glycolysis, the Krebs cycle, and the electron transport chain. When glucose is oxidized, it undergoes a series of chemical reactions that ultimately release energy. This energy is then captured in the form of adenosine triphosphate (ATP) as adenosine diphosphate (ADP) is phosphorylated to form ATP.

The process begins with glycolysis, where glucose is split into two molecules of pyruvate, generating a small amount of ATP and NADH in the process. Next, in the Krebs cycle, pyruvate is further oxidized and more electron carriers like NADH and FADH2 are produced. Finally, the electron transport chain uses these electron carriers to generate a large amount of ATP through oxidative phosphorylation, as protons are pumped across a membrane, creating an electrochemical gradient that drives ATP synthesis.

In contrast, the other choices do not accurately describe the primary mechanism of energy release in cellular respiration. While proteins and fats can also be metabolized for energy, the core pathway under discussion focuses on glucose breakdown as the primary source during cellular respiration. The statement regarding direct energy conversion from light