Biology 9700/23 May June 2012 | Cambridge AS Level Past Papers With Mark Scheme

1. Structural analysis of blood vessels: identification of vessel type, lumen diameter measurement, and roles of endothelial cells and elastic fibers.

2. Water uptake investigation using a potometer: temperature and environmental factors influencing transpiration rates, and its inevitable role in plant gas exchange.

3. Cholera toxin mechanism: interaction with epithelial ion channels, resulting in ion and water efflux, and explanation of transmission and outbreak factors.

4. DNA functionality: importance of hydrogen bonding in base pairing, stability of DNA, and labile nature of mRNA for gene regulation.

5. Malaria vaccine research: targeted use of parasite forms, antibody production process, and rationale for radioactive parasite inactivation.

6. Catfish pond ecosystems: producer role of phytoplankton, energy transfer efficiency, and biomass increase differences between wild and controlled environments.