Amino end and carboxyl end can be ionised NH³⁺ and COO^- to give acidic and basic characteristics. At pH 7 both groups are ionised.

The residues are side chains which give the individual properties to the amino acid (acidic, basic, neutral and nonpolar).

Functions of amino acids:

• protein synthesis
• energy reserve
• hormones (thyroxin)

20 different amino acids used in protein synthesis though others do occur in nature.

Essential amino acids cannot be synthesised by the organism and must form part of their diet.

Carboxyl group + amino group form a strong covalent bond releasing water in to process water = a condensation reaction (the reverse is hydrolysis).

Amino acids join together in a long chain: N terminal end to C terminal end = a polypeptide.

Protein structure determines protein function. Denaturation or inhibition which may change protein structure will change its function. Coenzymes and cofactors in general may enhance the protein's structure.

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