O Level Biology Practical 2020 Answers [best] Jun 2026

Changes from light blue to purple/violet.

Procedure : Add equal volumes of Benedict's solution and the sample into a test tube. Heat in a boiling water bath for 3–5 minutes.

The mark scheme would accept answers like "slightly brown" for "pale brown". The key is to show a progression. The table clearly demonstrates that the HCl-treated slice (A) remained yellow, showing the acid prevented browning, while the other two slices progressively turned brown. o level biology practical 2020 answers

Suggesting improvements to experiments, such as using a buffer solution to control pH. Final Thoughts for 2026 Candidates

Perform a Benedict's test on samples labeled A–E to estimate glucose concentration. Common Results: Changes from light blue to purple/violet

High temperature breaks hydrogen bonds in the enzyme’s tertiary structure, altering the active site so substrate cannot bind (denaturation).

How does pH/temperature affect rate of oxygen bubble production? The mark scheme would accept answers like "slightly

Use clear, continuous lines without shading and include a magnification calculation .

The experiment compared the growth of seedlings in the light versus the dark. One of the first questions asked you to identify other factors that must be kept constant.

Failing to insulate a test tube during an exothermic reaction.

This task required observing 15 seedlings grown in light and 15 grown in the dark. Stem Length