Explain how water acts as a metabolite in living organisms, giving two distinct examples of reactions in which water is either produced or consumed.

Water is a metabolite because it is directly involved as a reactant or product in metabolic reactions, not just as a solvent.
1. Hydrolysis – water is consumed. For example, the hydrolysis of a peptide bond in a polypeptide:
peptide + H₂O → two amino acids
or the hydrolysis of a triglyceride:
triglyceride + 3 H₂O → glycerol + 3 fatty acids.
2. Condensation – water is produced. For example, the formation of a peptide bond between two amino acids:
amino acid + amino acid → dipeptide + H₂O
or the synthesis of a glycosidic bond between two monosaccharides:
monosaccharide + monosaccharide → disaccharide + H₂O.
3. Photosynthesis – water is a reactant. In the light‑dependent reactions, water is split (photolysis) to give O₂, electrons and protons:
2 H₂O → 4 H⁺ + 4 e⁻ + O₂.
The electrons and protons are then used in the electron transport chain and to reduce NADP⁺ to NADPH.