Biology · Oct / Nov 2025 · Paper 62 · Question 1

A student investigated the rate of respiration in yeast using different concentrations of glucose. They used a 5% glucose solution to make a 1% glucose solution and a 4% glucose solution. The student used this method: Step 1 Label two small test-tubes 1% and 4%. Step 2 Use a syringe to put 1 cm3 of 5% glucose solution into the small test-tube labelled 1%. Put 4 cm3 of 5% glucose solution into the small test-tube labelled 4%. Step 3 Use a clean syringe to put 4 cm3 of distilled water into the small test-tube labelled 1%. Put 1 cm3 of distilled water into the small test-tube labelled 4%. Step 4 Pour yeast suspension into the small test-tube labelled 1% until it is completely full. Step 5 Keep the small test-tube upright and carefully place a large test-tube over the top of the small test-tube labelled 1%. Push the small test-tube up to the top of the large test-tube, as shown in Fig. 1.1A. Quickly invert the test-tubes, as shown in Fig. 1.1B. finger holding the small test-tube in position while the test-tubes are inverted B C A water-bath containing warm water large test-tube small test-tube containing yeast suspension and glucose solution Fig. 1.1 Step 6 Put the large test-tube and the small test-tube labelled 1% into a warm water-bath, as shown in Fig. 1.1C. Step 7 Start the stop-clock and wait for five minutes. 3 Step 8 After five minutes, stop the stop-clock and use a ruler to measure the height of the yeast suspension in the large test-tube, as shown in Fig. 1.2. height of the yeast suspension in the large test-tube after five minutes Fig. 1.2 Step 9 Remove the test-tubes from the warm water-bath and discard them. Step 10 Pour yeast suspension into the small test-tube labelled 4% until it is completely full. Step 11 Repeat steps 5 to 8 with the small test-tube labelled 4%.

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