Biology 9700/03 Oct Nov 2001 | Cambridge AS Level Past Papers With Mark Scheme

1. Urease Enzyme Experiment:
- Effect of temperature on urease activity measured by titration of ammonium carbonate.
- Variables not controlled: initial temperature fluctuations and timing precision during enzymatic reactions.
- Suggestions for improved reliability: replicate trials, ensure precise temperature control, and extend reaction observation periods.

2. Microscopy Analysis of Plant Stem:
- Drawing vascular bundle outlines accurately to represent size and position differences in a transverse section.
- Longitudinal section position inference based on observed alignment and structural patterns in both slides.

3. Enzyme Reaction Factors:
- Extended high-temperature exposure reduces enzyme activity due to denaturation.
- Short temperature exposure preserves activity but limits full reaction progression.

4. Microscopy Interpretation:
- Variability in section orientation influencing structural observations; highlighting importance of slide preparation accuracy.