Biosynthesis

Scheme for metabolism in organisms that use organic nutrients as a source of food. Block arrows indicate flow of carbon-containing molecules, red, use of ATP, green, used of reducing power (hydrogen). The position of biosynthesis as a distinct stage in assembly of cell components is indicated. (After schemes developed by F. Harold, M. Schaechter and others.)

Biosynthesis is an essential stage in metabolism where building blocks used in the synthesis of cell macromolecules and membranes are produced from simpler precursors. It is preceded by a fueling (catabolism stage and followed by polymerisation and assembly of building blocks into cell components.

Biosynthesis, takes place within living cellss and is generally catalysed by enzymes. The reactions are generally organised in sequential steps called biosynthetic pathways, which branch from a metabolic network known as central metabolism.

The prerequisites for biosynthesis are:

• Thirteen precursor carbon-skeletons
• Energy (usually in the form of ATP)
• Enzyme catalysts
• Reduction equivalents (in the form of hydrogen carried on the coenzymes NADH, NADPH and others)
• Nitrogen in the form of ammonium ion.
• Reduced forms of sulfur in some amino acids

Important and widely known products of biosynthesis include amino acids, nucleotides, and , vitamins but all components of living beings depend on this process. Biosynthesis is harvested by the biotechnology industry to manufacture flavoring compounds such as mono sodium glutamate and lysine, vitamins, and therapeutic proteins such as insulin and growth hormones.

Representive biosynthetic pathway

The amino acid glutamate is a common component of proteins. It can be formed by a short pathway that illustrates the features of a typical biosynthetic pathway.

File:Glutamate biosynthesis2.jpg

Glutamate formation via glutamine in two steps. This pathway is an important physiological adaptation to survival whe ammonia is limiting for many microrganisms as it enable capture of ammonia at low concentrations for many biosynthetic products. Glutamate is able to transfer its amino group to many different nitrogen containing compounds in the cell.