Elektrontransportahel

Elektrontransportahel, also known as the electron transport chain (ETC), is a series of protein complexes embedded in the inner mitochondrial membrane of eukaryotic cells and the plasma membrane of prokaryotic cells. Its primary function is to facilitate the transfer of electrons from electron donors to electron acceptors through a series of redox reactions. This process is crucial for cellular respiration, the metabolic pathway that converts chemical energy stored in glucose and other fuel molecules into adenosine triphosphate (ATP), the main energy currency of the cell.

The ETC is composed of several key components, including NADH dehydrogenase (Complex I), succinate dehydrogenase (Complex II), ubiquinone (Coenzyme Q), cytochrome c reductase (Complex III), cytochrome c, and cytochrome c oxidase (Complex IV). Electrons are initially passed from NADH and FADH2, which are produced during earlier stages of cellular respiration like glycolysis and the Krebs cycle, to Complex I and Complex II respectively. From these complexes, electrons are shuttled through ubiquinone to Complex III, then to cytochrome c, and finally to Complex IV.

As electrons move through these complexes, energy is released. This energy is utilized by Complexes I, III, and IV to pump protons (H+) from the mitochondrial matrix into the intermembrane space. This creates an electrochemical gradient across the inner mitochondrial membrane. The potential energy stored in this proton gradient is then harnessed by ATP synthase, a separate enzyme complex, which uses the flow of protons back into the matrix to synthesize ATP from ADP and inorganic phosphate. This process is called chemiosmosis. The final electron acceptor in aerobic respiration is oxygen, which combines with electrons and protons to form water.