Respiration — practice question

A student studied how the rate of respiration in yeast changed with different glucose concentrations. A 5% glucose solution was used to prepare both a 1% glucose solution and a 4% glucose solution. The student carried out the method below: Step 1 Label two small test-tubes 1% and 4%. Step 2 With a syringe, place 1 cm^{3} of 5% glucose solution into the small test-tube marked 1%. Place 4 cm^{3} of 5% glucose solution into the small test-tube marked 4%. Step 3 Using a clean syringe, add 4 cm^{3} of distilled water to the small test-tube marked 1%. Add 1 cm^{3} of distilled water to the small test-tube marked 4%. Step 4 Add yeast suspension to the small test-tube marked 1% until it is filled completely. Step 5 Keep the small test-tube upright and gently put 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. 1.1B. Quickly turn the test-tubes upside down, as shown in Fig. 1.1B. Fig. 1.1 labels: large test-tube; small test-tube containing yeast suspension and glucose solution; finger holding the small test-tube in position while the test-tubes are inverted; water-bath containing warm water. Step 6 Place the large test-tube and the small test-tube labelled 1% in a warm water-bath, as shown in Fig. 1.1C. Step 7 Start the stop-clock and leave it for five minutes. 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. Fig. 1.2 label: height of the yeast suspension in the large test-tube after five minutes. Step 9 Take the test-tubes out of the warm water-bath and throw them away. Step 10 Add yeast suspension to the small test-tube labelled 4% until it is filled completely. Step 11 Repeat steps 5 to 8 with the small test-tube labelled 4%.