hengitysketjussa

Hengitysketju, or the "respiratory chain," refers to a series of protein complexes and molecules located in the inner mitochondrial membrane of eukaryotic cells. It plays a crucial role in cellular respiration by facilitating the transfer of electrons from electron donors to electron acceptors via redox reactions. This process generates a proton gradient, which drives ATP synthesis—the primary energy currency of the cell.

The respiratory chain is composed of four main complexes: Complex I (NADH dehydrogenase), Complex II (succinate dehydrogenase), Complex III (cytochrome bc₁ complex), and Complex IV (cytochrome c oxidase). Additionally, two mobile electron carriers, ubiquinone (coenzyme Q) and cytochrome c, shuttle electrons between these complexes. Electrons are initially derived from NADH and FADH₂, produced during glycolysis, the Krebs cycle, and other metabolic pathways.

As electrons move through the chain, protons are pumped from the mitochondrial matrix into the intermembrane space, creating an electrochemical gradient. This gradient is harnessed by ATP synthase (Complex V) to phosphorylate ADP into ATP, a process known as oxidative phosphorylation. The efficiency of this process is essential for cellular energy production, particularly in high-energy-demand tissues like the brain and muscles.

Disruptions in the respiratory chain can lead to various mitochondrial disorders, affecting energy metabolism and contributing to diseases such as muscular dystrophy, neurodegenerative conditions, and metabolic syndromes. Research into the respiratory chain continues to provide insights into mitochondrial function, bioenergetics, and potential therapeutic targets for related disorders.