Biology 9700/21 May June 2010 | Cambridge AS Level Past Papers With Mark Scheme

1. Sucrose hydrolysis: glycosidic bond identification, roles of water in hydrolysis, and enzymatic catalysis by sucrase.

2. Alveolar adaptations for gas exchange: elastic fiber function, surface area optimization, and emphysema's effects on alveolar structure and lung function.

3. Cardiac cycle: valve functions ensuring one-way blood flow, pressure changes in left atrium and ventricle, and electrical coordination by SAN, AVN, and Purkyne fibers.

4. Infectious diseases: malaria transmission by Anopheles mosquitoes, TB's global distribution due to airborne transmission, and vaccination programs' roles in disease control.

5. DNA replication: semi-conservative mechanism, nitrogenous base pairing, and proofreading enzyme importance for genetic consistency post-mitosis.

6. Nitrogen cycle in legume ecosystems: roles of Rhizobium bacteria in nitrogen fixation, ammonia conversion, and nitrate synthesis aiding legume growth in nutrient-poor soils.