Explain the key event that occurs when a condensation reaction joins or hydrolysis splits building-block molecules of carbohydrates, lipids, or proteins.
When a condensation reaction joins the building-block molecules of carbohydrates, lipids, or proteins, one molecule of water is removed from each union between two building-block molecules. When two monosaccharides are joined, the molecule of water is removed from two adjacent hydroxyl groups (OH), leaving both molecules covalently bonded to the remaining oxygen. When a fatty acid molecule is joined to glycerol, the molecule of water is removed from the fatty acid's carboxyl group (COOH) and an adjacent hydroxyl group of the glycerol, leaving both molecules covalently bonded to the remaining oxygen. When two amino acids are joined, the molecule of water is removed from a carboxyl group and an amino group ( ) that are adjacent to each other, creating a covalent bond between the former carboxyl group's carbon and the former amino group's nitrogen. When hydrolysis splits complex molecules into simpler components, a molecule of water must be added for every split between two building-block molecules.
