Metabolism
Metabolism is the full network of enzyme-driven chemical reactions that lets cells capture energy, build molecules, break down fuels, and maintain life.
What metabolism is
Metabolism is the organized chemistry of life. It includes all the reactions that let a cell obtain energy, transform nutrients, build structures, recycle parts, remove waste, and respond to changing conditions.
Catabolism breaks down
Catabolic pathways break larger molecules into smaller ones. They often release usable energy or reducing power. Cellular respiration, fermentation, digestion of food molecules, and many fuel-oxidation pathways are catabolic in broad terms.
Anabolism builds up
Anabolic pathways use energy and raw materials to make larger or more organized molecules. Cells use anabolism to build proteins, nucleic acids, lipids, carbohydrates, cell walls, pigments, storage compounds, and many specialized chemicals.
Enzymes make pathways controllable
Metabolism is not a random soup of reactions. Enzymes guide reactions through pathways, lower activation energy, and allow cells to regulate rates. Feedback inhibition, gene regulation, allosteric control, and compartmentalization help keep pathways coordinated.
ATP and carriers move energy
ATP often transfers usable energy to cell work, but it is only one part of the system. NADH, FADH2, NADPH, ion gradients, and activated chemical intermediates also help move electrons, phosphate groups, carbon fragments, and reducing power through metabolism.
Metabolism is networked
Pathways share intermediates. A molecule from sugar breakdown may feed amino-acid synthesis. A fatty-acid pathway may depend on reducing power from another route. This network structure lets cells adapt, but it also means one bottleneck can affect many processes.
Why it matters
Metabolism explains how food becomes cell work, how sunlight becomes biomass, how microbes reshape ecosystems, and how inherited or acquired pathway problems can affect health. It is the bridge between chemistry and living behavior.