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Paper 1
Organisation
Both
Trace the path of food and name each organ.
Key Facts
- Tissues form organs, organs form organ systems.
- Enzymes are biological catalysts with an optimum temperature and pH.
- The heart has four chambers and valves to keep blood flowing one way.
- Alveoli are surrounded by capillaries for rapid gas exchange.
Topics Covered
Digestive System
What you need to know
- •Enzymes break food into small, soluble molecules.
- •Bile neutralises acid and emulsifies fats.
Exam Tips
- For digestion questions, mention enzyme names and substrates.
Enzymes
What you need to know
- •Enzymes have an active site that fits one substrate.
- •Temperature and pH affect enzyme activity.
Exam Tips
- Use "optimum" and "denature" in 4-6 mark answers.
Circulatory System
What you need to know
- •Arteries carry blood away from the heart; veins carry blood to it.
- •Capillaries have thin walls for exchange.
Exam Tips
- Use the word "exchange" for capillaries and "pressure" for arteries.
Respiratory System
What you need to know
- •Alveoli provide a large surface area for gas exchange.
- •Ventilation maintains concentration gradients in the lungs.
Exam Tips
- Link surface area, thin walls, and blood supply to diffusion.
Key Terms
Enzyme
A biological catalyst that speeds up reactions.
Villi
Finger-like structures in the small intestine that increase surface area.
Substrate
The molecule that an enzyme acts on.
Alveoli
Air sacs where gas exchange happens in the lungs.
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Common Exam Questions
Describe two adaptations of the small intestine for absorption.
4 marksmediumPaper 1
Model Answer
Villi and microvilli give large surface area; good blood supply maintains a steep concentration gradient.
What examiners want to see
- ✓Surface area.
- ✓Blood supply or thin walls.
Explain why enzyme activity falls at high temperatures.
3 marksmediumPaper 1
Model Answer
High temperatures denature enzymes, changing the active site so the substrate no longer fits.
What examiners want to see
- ✓Use the word denature.
- ✓Explain active site shape changes.
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