Biomolecules can be acid insoluble i.e. macromolecules or acid soluble i.e. micromolecules. Macromolecules are carbohydrates, proteins, lipids and nucleic acids. Proteins contain many amino acids that are linked by peptide bonds and are known as polypeptides. Amino acids contain two functional groups which can form ions. Enzymes are tertiary structure of proteins.