IGCSE Biology glossary
Amino acid
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
A small organic molecule that is the monomer of proteins. Twenty different amino acids exist, and they are joined together by peptide bonds during protein synthesis at ribosomes. The sequence of amino acids determines the shape and function of the protein.
What to include in an exam answer
In digestion questions, say proteins are broken down into amino acids, not 'broken up' or 'dissolved'. Amino acids are absorbed into the blood and reassembled into new proteins in cells.
Example in context
Describe what happens to protein molecules during digestion (2 marks): Proteins are broken down by protease enzymes into amino acids, which are small enough to be absorbed into the blood through the wall of the small intestine.
Related syllabus topic
Biological molecules