Cambridge IGCSE·Co-ordinated Sciences 0654·Biology
Biological Molecules
Key knowledge — Biological Molecules
Key facts & rules
- Carbohydrates: made of C, H, O. Glucose (C₆H₁₂O₆) is a monosaccharide.
- Glucose + Glucose → Maltose (disaccharide) + water (condensation).
- Starch and glycogen are polysaccharides (storage) made of glucose monomers.
- Proteins: made of amino acid monomers joined by peptide bonds. Contain C, H, O, N (and sometimes S).
- Lipids (fats/oils): made of glycerol + 3 fatty acids. Insoluble in water.
- Test for starch: iodine solution — blue-black if positive.
- Test for reducing sugars: Benedict's solution — brick-red precipitate if positive.
- Test for protein: Biuret solution — purple/violet if positive.
- Test for lipids: ethanol emulsion test — milky-white emulsion if positive.
IGCSE Biology — Biological molecules
1574 Cambridge IGCSE 0654 biology past paper questions on biological molecules, organised by subtopic. Pick a subtopic to start practising.
About biological molecules on IGCSE 0654
Carbohydrates, proteins, lipids and water, the chemical elements they contain, and the food tests for starch, reducing sugars, protein and fats.