Exercise 1 — IGCSE 0653 Oct/Nov 2023 Paper 42 Q4
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any three from:
Cambridge IGCSE·Combined Sciences 0653·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
3 Cambridge IGCSE 0653 Combined Sciences past paper questions on biological molecules, across Theory, Multiple Choice and Alternative to Practical.
About Biological Molecules on IGCSE 0653
Carbohydrates, proteins and lipids are the main biological molecules. Students learn how glucose, starch and glycogen relate to each other, how amino acids form proteins, and the role of glycerol and fatty acids in lipids.
What's covered:
- Carbohydrates: glucose, sucrose, starch, glycogen
- Proteins and amino acids
- Lipids: glycerol and fatty acids
- Monomers and polymers
- Testing for biological molecules
Theory
Biological Molecules — Extended1 · Paper 4
Alternative to practical
Biological Molecules — ATP2 questions
Exercise 1 — IGCSE 0653 May/Jun 2025 Paper 52 Q1
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size: drawing fills more than 50% of available space
Exercise 2 — IGCSE 0653 May/Jun 2025 Paper 62 Q1
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size: drawing fills more than 50% of available space
All Biological Molecules questions in this collection
| Type | Level | Paper | Session | Q# | Marks | Answer / key |
|---|---|---|---|---|---|---|
| ATP | Core | Paper 52 | May/Jun 2025 | Q1 | 13 marks | size: drawing fills more than 50% of available space |
| ATP | Extended | Paper 62 | May/Jun 2025 | Q1 | 13 marks | size: drawing fills more than 50% of available space |
| Theory | Extended | Paper 42 | Oct/Nov 2023 | Q4 | 12 marks | any three from: |