a) Proteins, which are highly-folded poplypeptides, are broken down into shorter polypeptides, and then into amino acids, by protease enzymes.
b) Fats, or lipids, are broken down by enzymes such as lipase into fatty acids and glycerol.
c) Carbohydrates are sugars - sugars that are usually in the form of polymers (made up of many smaller sugar monomers) when they are eaten. They are broken down into disaccharides (such as lactose) and then into monosaccharides (such as glucose and galactose that make up lactose) by an enzyme, such as lactase.