Biology 9700/21 Oct Nov 2009 | Cambridge AS Level Past Papers With Mark Scheme

1. Antibody structure and immune response mechanisms: variable region identification, importance of disulfide bonds for structural stability, and antibody-mediated pathogen neutralization.

2. Amylase activity experiment: pH effects on starch hydrolysis, reaction rate trends across pH levels, and optimal conditions for enzymatic function.

3. Mitosis observation: electron micrograph analysis of lymphocyte division, limitations of electron microscopy for dynamic processes, and tumor development in lung tissue from prolonged smoking.

4. Transpiration in plants: comparative rates between species, potential adaptations (e.g., stomatal density, waxy cuticle), and their roles in reducing water loss.

5. Opportunistic infection by Pneumocystis jirovecii: life cycle stages, structural features of eukaryotes, transmission methods, and challenges in controlling HIV/AIDS spread.

6. River ecosystem energy dynamics: energy transfer efficiency across trophic levels, decomposer roles in nitrogen cycling, and producer-consumer interactions sustaining the food web.