Biology 9700/03 May June 2003 | Cambridge AS Level Past Papers With Mark Scheme

1. Yeast respiration experiment: bubble count used to measure CO\\(_2\\) production at different temperatures, with results recorded for boiling tubes containing yeast-glucose solution (T1) and water (T2).

2. Water-bath setup: temperatures maintained at 35–40°C and 45–50°C to assess enzyme activity changes, emphasizing optimal and denaturing conditions.

3. T2 control: validation of results by comparing bubbling rates in a solution lacking active respiration, ensuring reliability of T1 observations.

4. Procedure improvements: standardizing timing, consistent water-bath temperatures, and automated bubble counting for enhanced accuracy.

5. Mammalian lung structure: high-power drawing of alveolar wall junction, detailing epithelial cells, connective tissue, and capillaries.

6. Ratio measurement: eyepiece graticule used to determine the ratio of alveolar diameter to wall thickness, focusing on procedural accuracy in microscopy.