Biology 9700/02 May June 2005 | Cambridge AS Level Past Papers With Mark Scheme

1. DNA replication: semi-conservative mechanisms explained by complementary base pairing; importance of accuracy to prevent mutations.

2. Transverse leaf section labeled with xylem, phloem, and mesophyll cells; water movement from vascular tissue to atmosphere via water potential gradient.

3. Hemoglobin's quaternary structure facilitates oxygen binding in lungs; CO₂-induced oxygen release explained by Bohr effect.

4. Collagen synthesis: polypeptide formation, secretion, and extracellular fiber assembly; enzyme specificity for peptide bond hydrolysis.

5. Energy transfer inefficiency in ecosystems: low producer-to-consumer energy conversion; nitrogen cycling from proteins to plant-available forms.

6. Blood, tissue fluid, and lymph comparison; cardiovascular effects of nicotine, including increased heart rate and blood pressure.

7. Smoking and lung cancer correlation: male prevalence in high-smoking populations; regional variations linked to smoking intensity and lifestyle.