metabolizing

Metabolizing refers to the set of biochemical processes by which living organisms transform chemical substances to sustain life. These processes convert nutrients from food into energy and cellular components, synthesize complex molecules, and detoxify or eliminate foreign compounds.

Metabolism comprises two broad classes: catabolism, the breakdown of molecules to release energy, and anabolism, the synthesis of larger molecules from smaller ones. Enzymes drive most steps, with energy captured as ATP. Major pathways include glycolysis, the citric acid cycle, and oxidative phosphorylation for carbohydrate processing, plus fatty acid oxidation and amino acid metabolism. Other pathways support glucose production and storage, such as gluconeogenesis and glycogenesis.

In humans, the liver is the primary site of metabolizing for many compounds, including drugs. Reactions are often grouped into Phase I (functionalization) and Phase II (conjugation). Phase I uses enzymes like cytochrome P450s to introduce reactive groups; Phase II adds conjugates to increase solubility for excretion. Metabolites may be active, inactive, or toxic. Drug metabolism influences duration of action and the first-pass effect, with excretion typically via kidneys or bile.

Metabolic rate—the speed of metabolic processes—varies with age, sex, body size, hormones, nutrition, activity, and genetics. Disease, such as liver or kidney impairment, can reduce metabolizing capacity. Inborn errors of metabolism are inherited disorders that disrupt specific pathways. Metabolism also governs detoxification of environmental chemicals and energy balance.

Examples include glucose to pyruvate in glycolysis, ethanol to acetaldehyde and acetate in alcohol metabolism, and lipid breakdown for energy. Metabolites are excreted in urine or feces after processing in the liver and kidneys.