Cell metabolism is the process (or really the sum of many ongoing individual processes) by which living cells process nutrient molecules and maintain a living state. Metabolism has two distinct divisions: anabolism, in which a cell uses energy and reducing power to construct complex molecules and perform other life functions such a creating cellular structure; and catabolism, in which a cell breaks down complex molecules to yield energy and reducing power. Cell metabolism involves extremely complex sequences of controlled chemical reactions called metabolic pathways.
Anabolism is a constructive metabolic process whereby energy is consumed to synthesize or combine simpler substances, such as amino acids, into more complex organic compounds, such as enzymes and nucleic acids.
Catabolism is a type of metabolic process occurring in living cells by which complex molecules are broken down to produce energy and reducing power. On balance, catabolic reactions are normally exothermic.
Main article: Carbohydrate catabolism
Carbohydrate catabolism is the breakdown of carbohydrates into smaller units. The empirical formula for carbohydrates, like that of their monomer counterparts, is CX(H2YOY). Carbohydrates literally undergo combustion to retrieve the large amounts of energy in their bonds. Read more about mitochondria to find out more about the reaction and how its energy is secured in ATP.
Main article: Fat catabolism
Fat catabolism, also known as lipid catabolism, is the process of lipids or phospholipids being broken down by lipases. The opposite of fat catabolism is fat anabolism, involving the storage of energy, and the building of membranes.
Main article: Protein catabolism
Protein catabolism is the breakdown of proteins into amino acids and simple derivative compounds, for transport into the cell through the plasma membrane and ultimately for the polymerisation into new proteins via the use of ribonucleic acids (RNA) and ribosomes.