Metabolism, also known as catabolism and anabolism, refers to the sum of all chemical reactions occurring within an organism that enable it to sustain life, grow, and reproduce. Metabolism is categorized into two fundamental types: anabolism and catabolism. Anabolism is the constructive phase of metabolism, where small molecules are synthesized into larger molecules. This process requires energy, typically derived from nutrients obtained through food. Catabolism is the breakdown phase, where large molecules are decomposed into smaller molecules, releasing energy. This energy is essential for maintaining fundamental bodily functions such as movement, temperature regulation, and cell repair. Beyond energy production and consumption, metabolism also involves nutrient transport and excretion, temperature regulation, and adaptation to environmental changes.