Biology 9700/12 Oct Nov 2009 | Cambridge AS Level Past Papers With Mark Scheme

1. Electron microscopy visualization: structures like ribosomes, chromosomes, and nucleoli identified at cellular levels.

2. Prokaryotic cell characteristics: absence of a nucleus, division by binary fission, and presence of ribosomes.

3. Protein bonds stabilizing structures: weak hydrogen bonds, strong disulfide bonds, and ionic interactions ensuring tertiary stability.

4. Collagen tensile strength: covalent cross-links, triple helix structure, and small glycine residues for compact arrangements.

5. Enzymatic activity and hydrolysis mechanisms: tripeptide breakdown and protein active site structural control.

6. Energy transfer efficiency in ecosystems: trophic levels, net primary production calculations, and energy loss across consumers.

7. Semi-conservative DNA replication: Meselson-Stahl experiment evidence, nucleotide pair consistency, and enzymatic proofreading.

8. Photosynthesis and translocation: sucrose loading into phloem via companion cells, hydrostatic pressure gradients, and mass flow to sinks.

9. Immune system dynamics: primary and secondary responses, B-lymphocyte activation, and antibody production cycles.

10. Arctic ecosystem trophic structure: phytoplankton as producers, multi-level consumers like polar bears, and energy flow through the food web.