Cellular bioenergetics: Glycolysis, oxidative phosphorylation, and lipid metabolism pathways

Cellular bioenergetics is the foundation for understanding how cells acquire, store, and use energy to maintain vital functions. This process primarily involves the metabolic pathways of lipid metabolism, oxidative phosphorylation, and glycolysis. Glycolysis functions to break down glucose in the cytoplasm, producing pyruvate and NADH as the initial energy source. The Krebs cycle in the mitochondria subsequently breaks down pyruvate further, generating reductants that aid in oxidative phosphorylation. At this point, the proton gradient is effectively used by the electron transport chain to transform chemical energy into ATP. The Krebs cycle and oxidative phosphorylation are triggered by the massive amounts of acetyl-CoA, NADH, and FADH₂ that are produced by lipid metabolism through lipolysis and β-oxidation. Energy sensors like AMPK and mTOR are involved in this extremely tight cross-pathway control, which synchronizes the balance between anabolism and catabolism based on the energy condition of the cell. Cells can adapt to a variety of physiological situations, including rest, exercise, and fasting, thanks to the integration of glucose and lipid metabolism. Many metabolic and degenerative diseases, including diabetes, obesity, cancer, and mitochondrial disorders, are caused by bioenergetic dysfunctions, such as abnormalities in glycolysis, lipid oxidation, or oxidative phosphorylation. Thus, in addition to being crucial for physiological aspects, a thorough understanding of bioenergetic mechanisms and controls also creates prospects for the development of therapeutic approaches based on metabolism.