Biosynthesis

Biosynthesis is the cellular process by which complex organic molecules are produced from simpler precursor molecules. It is a central component of metabolism and is typically classified as anabolism, in contrast to catabolism, which breaks down substances. Biosynthesis requires energy, usually in the form of ATP, and reducing power such as NADPH, and it is mediated by networks of enzymes that assemble, modify, and couple small building blocks into larger biomolecules.

Major groups of biosynthesis include primary metabolism, which produces essential macromolecules such as amino acids, nucleotides, sugars, lipids, and cofactors, and secondary (specialized) metabolism, which yields compounds not strictly necessary for growth but important for ecological interactions. These include alkaloids, terpenoids, phenolics, polyketides, and siderophores.

Key pathways provide carbon skeletons and reducing equivalents for biosynthesis. Photosynthesis and carbon fixation generate foundational carbon units in plants and photosynthetic microbes. Central metabolism, including glycolysis, gluconeogenesis, and the pentose phosphate pathway, supplies precursors and reducing power. Fatty acid, nucleotide, and amino acid biosynthesis build lipids, nucleotides, and proteins, while isoprenoid and polyketide pathways produce a wide range of specialized metabolites.

Enzymes orchestrate each step, and regulation occurs through feedback inhibition, transcriptional control, and allosteric effects to maintain cellular homeostasis. Biosynthesis is universal across life, enabling growth, maintenance, and interaction with the environment. In biotechnology, engineered biosynthetic pathways are used to produce vitamins, amino acids, biofuels, and therapeutic compounds, highlighting the practical importance of understanding these processes.