Metabólismi

Metabólismi, or metabolism, refers to the set of life-sustaining chemical reactions that occur in organisms. It encompasses two major classes: catabolic pathways that break down molecules to harvest energy and building blocks, and anabolic pathways that synthesize complex molecules from simpler precursors using energy. Together, these processes power growth, maintenance, and responses to the environment.

Central metabolism includes pathways that convert nutrients into usable energy and biosynthetic precursors. Glycolysis breaks down sugars in the cytoplasm and generates energy and reducing equivalents. The pyruvate dehydrogenase step links glycolysis to the citric acid cycle, which, in turn, feeds into oxidative phosphorylation to produce most cellular ATP. In photosynthetic organisms, light-driven reactions capture energy and fix carbon to build organic molecules.

Metabolic reactions are tightly regulated by enzymes and the cell’s energy status. Regulation occurs through allosteric control, covalent modification, and changes in gene expression. Hormones such as insulin, glucagon, and adrenaline coordinate metabolism in multicellular organisms, balancing energy storage, mobilization, and substrate availability. Feedback mechanisms ensure metabolic flux aligns with physiological needs.

Metabolism varies across organisms and conditions, reflecting differences in diet, environment, and evolutionary history. Disruptions in metabolic pathways underlie many diseases, ranging from inherited metabolic disorders to common conditions like diabetes. Modern fields such as metabolomics study the network of small molecules produced by metabolism, contributing to understanding physiology, nutrition, and disease.