IGCSE Biology glossary
Starch
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 complex carbohydrate (polysaccharide) used as the main energy storage molecule in plants. It is made of long chains of alpha-glucose molecules and is insoluble in water, making it ideal for storage because it does not affect the water potential of cells.
What to include in an exam answer
Starch is tested with iodine solution, which turns from brown/yellow to blue-black. This is the single most frequently tested food test. Remember starch is a plant storage molecule; animals store glycogen.
Example in context
Explain why starch is a suitable storage molecule (2 marks): Starch is insoluble, so it does not affect the water potential of cells, and it is compact, so large amounts can be stored in a small space.
Related syllabus topic
Biological molecules