Biosynthesis is a process in which substrates are converted into more complex products through chemical reactions that are enzyme-catalyzed in living organisms/05%3A_Microbial_Metabolism/5.12%3A_Biosynthesis/5.12B%3A_Biosynthesis_and_Energy). This process often consists of metabolic pathways, which involve the modification, conversion, or joining of simple compounds to form macromolecules. Some examples of biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism, which is the branch of metabolism that results in the production of complex molecules from simpler substances/05%3A_Microbial_Metabolism/5.12%3A_Biosynthesis/5.12B%3A_Biosynthesis_and_Energy). The prerequisite elements for biosynthesis include precursor compounds, chemical energy (e.g. ATP), and catalytic enzymes, which may need coenzymes (e.g. NADH, NADPH) . These elements create monomers, the building blocks for macromolecules. Some important biological macromolecules include proteins, which are composed of amino acid monomers joined via peptide bonds, and DNA molecules, which are composed of nucleotides joined via phosphodiester bonds.