Biosynthesis is a phenomenon where chemical compounds are produced from simpler reagents. Biosynthesis, unlike chemical synthesis, takes place within living organisms and is generally catalysed by enzymes. The process is vital part of metabolism.

The prerequisites for biosynthesis are:

• Precursor substances
• Energy (usually in the form of ATP)

Often required components include:

• Catalysts, usually enzymes
• Reduction equivalents (in the form of NADH, NADPH and others)

Important and commonly known products of biosynthesis include proteins, vitamins, and antibiotics, but all components of living beings are a result of this process. In the near future it may be possible, with the help of biotechnology, to harness this process for the production of e.g. biodegradable plastics.