Sejtmködést

Sejtmködést, often translated as cellular respiration, is a fundamental biological process that occurs in the cells of all living organisms. It is the mechanism by which organisms break down nutrient molecules, such as glucose, and release the stored energy in a form that can be used by the cell, primarily adenosine triphosphate (ATP). This process is essential for virtually all cellular activities, including muscle contraction, nerve impulse transmission, and the synthesis of new molecules.

Cellular respiration can be broadly divided into several stages. In eukaryotes, the initial stage, glycolysis, occurs in the cytoplasm and involves the breakdown of glucose into pyruvate. This is followed by the Krebs cycle (also known as the citric acid cycle) and oxidative phosphorylation, which take place within the mitochondria. During oxidative phosphorylation, a series of protein complexes embedded in the inner mitochondrial membrane utilize electrons to generate a proton gradient, which then drives ATP synthesis. In prokaryotes, which lack mitochondria, these later stages occur in the cytoplasm and across the cell membrane.

While glucose is the most common substrate for cellular respiration, other organic molecules, such as fats and proteins, can also be broken down and fed into the respiration pathway at various points. The overall process requires oxygen as a final electron acceptor in aerobic respiration, producing carbon dioxide and water as byproducts. Anaerobic respiration and fermentation are alternative pathways that can occur in the absence of oxygen, yielding less ATP and different byproducts.