Water takes part in metabolic reactions
Water is a metabolite because it participates directly in many reactions occurring in living organisms. It is particularly important in condensation and hydrolysis.
Condensation
During a condensation reaction, smaller molecules become joined by a chemical bond to form a larger molecule, and water is removed.
smaller molecules → larger molecule + water
Examples include formation of:
- peptide bonds when amino acids join
- glycosidic bonds in carbohydrates
- ester bonds in lipids
Hydrolysis
During hydrolysis, water is added as a bond in a larger molecule is broken, producing smaller molecules.
larger molecule + water → smaller molecules
Examples include breaking:
- proteins into amino acids
- starch into glucose
- triglycerides into fatty acids and glycerol
Water may therefore be either released or used during reactions that build up and break down biological molecules.