Biology 9700/02 Oct Nov 2002 | Cambridge AS Level Past Papers With Mark Scheme

1. Alveolus function: gas exchange through diffusion gradients for oxygen uptake and carbon dioxide release, facilitated by thin walls and capillary proximity.

2. Asthma mechanisms: immune response to allergens, histamine release causing inflammation, bronchiole narrowing, and mucus secretion obstructing airflow.

3. Triglyceride formation: ester bond synthesis via condensation reactions; advantages over carbohydrates in energy storage due to higher caloric density.

4. Xerophyte adaptations: thick cuticles and sunken stomata reducing transpiration rates, maintaining water balance in arid environments.

5. Enzyme activity: specificity from active site conformation, restriction enzyme recognition of palindromic DNA sequences, and DNA insertion into plasmids via complementary base pairing.

6. Malaria transmission: Plasmodium spread via mosquito bites; erythrocytic infection causing anemia and immune system stress from intracellular parasite replication.

7. Anaerobic respiration in muscles: lactate production under oxygen deficit, oxygen debt repayment post-exercise, and cardiovascular fitness assessment via pulse recovery rate.