Biology 9700/31 Oct Nov 2009 | Cambridge AS Level Past Papers With Mark Scheme

1. Sugar concentration estimation in phloem extract using Benedict’s test, serial dilutions, and color change timing in boiling water bath.

2. Plan diagram of transverse stem section and detailed high-power drawing of phloem cells, including companion cells.

3. Methylene blue staining in yeast: decolorization by living cells, observations in boiled yeast vs. glucose solution.

4. Yeast respiration: CO\\(_2\\) bubble counts under varying sodium chloride concentrations, mean activity calculation, and graphical analysis of salt concentration effects.

5. Differences in yeast activity between low and high sodium chloride concentrations explained by osmotic effects on cellular metabolism.

6. Improvements to experimental reliability: precise timing, temperature control, and standardization of staining or testing procedures.