Explain why lipids are described as being made from fatty acids and glycerol, and why proteins are described as being made from amino acids.

Lipids are large molecules that are made up of fatty acid chains attached to a glycerol backbone. The fatty acids are long hydrocarbon chains with a carboxyl group, and glycerol is a three‑carbon alcohol; ester bonds link them.

Proteins are also large molecules, but they are assembled from amino acids. Each amino acid has an amino group, a carboxyl group and a distinctive side chain, and peptide bonds join the amino acids into a chain.

Both lipids and proteins are macromolecules built from smaller sub‑units – fatty acids and glycerol for lipids, amino acids for proteins.