Sidrunhappetsükkel

Sidrunhappetsükkel, also known as the citric acid cycle or Krebs cycle, is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. This metabolic pathway occurs in the mitochondrial matrix of eukaryotic cells. The cycle begins with the combination of acetyl-CoA with oxaloacetate to form citrate. Through a series of enzymatic steps, citrate is progressively broken down, releasing carbon dioxide molecules and generating high-energy electron carriers, specifically NADH and FADH2. Additionally, a small amount of ATP (or GTP in some organisms) is produced directly through substrate-level phosphorylation. The primary purpose of the sidrunhappetsükkel is to provide these electron carriers for the subsequent electron transport chain, where the majority of ATP is generated. The cycle is a central hub in cellular metabolism, connecting various catabolic and anabolic pathways. Its regulation is tightly controlled to meet the energy demands of the cell.