Glycolysis, the Krebs cycle, and the electron transport chain are three interconnected metabolic pathways that play a critical role in cellular respiration, the process by which cells generate energy in the form of ATP.
- Glycolysis: Glycolysis is the first stage of cellular respiration and occurs in the cytoplasm of cells. During glycolysis, glucose is broken down into two molecules of pyruvate, producing a net yield of two molecules of ATP. Glycolysis also generates high-energy electrons in the form of NADH, which will be used in subsequent stages of cellular respiration.
- Krebs cycle: The Krebs cycle, also known as the citric acid cycle, occurs in the mitochondria of cells. During the Krebs cycle, the two molecules of pyruvate from glycolysis are further broken down into carbon dioxide, releasing energy in the form of ATP and NADH. The Krebs cycle also produces FADH2, another molecule that will be used in the electron transport chain.
- Electron transport chain: The electron transport chain occurs in the inner membrane of the mitochondria. During this stage, the high-energy electrons generated by glycolysis and the Krebs cycle are used to generate a proton gradient across the membrane. This gradient is then used by ATP synthase to produce ATP through oxidative phosphorylation. The electron transport chain also produces water as a byproduct of the reduction of oxygen.
Overall, these three metabolic pathways work together to generate a large amount of ATP from glucose, the primary fuel source for most cells. Disruptions in these pathways can lead to a variety of metabolic disorders and diseases, highlighting the importance of understanding their regulation and function.