A student investigated the effect of glucose concentration on the rate of anaerobic respiration in yeast. Anaerobic respiration in yeast breaks down glucose to form ethanol and carbon dioxide. Anaerobic respiration in yeast causes the blue dye, methylene blue, to become colourless. The time taken for the blue colour to disappear can be used as a measure of the rate of anaerobic respiration in yeast. The student used this method: Step 1 Label one test-tube $$\(0.0 \%\)$$, one test-tube $$\(0.5 \%\)$$ and one test-tube $$\(1.0 \%\)$$. Step 2 Put $$\(5.0 \mathrm{~cm}^{3}\)$$ of water into the test-tube labelled $$\(0.0 \%\)$$. Step 3 Put $$\(2.5 \mathrm{~cm}^{3}\)$$ of $$\(1.0 \%\)$$ glucose solution and $$\(2.5 \mathrm{~cm}^{3}\)$$ of water into the test-tube labelled $$\(0.5 \%\)$$. Step 4 Put $$\(5.0 \mathrm{~cm}^{3}\)$$ of $$\(1.0 \%\)$$ glucose solution into the test-tube labelled $$\(1.0 \%\)$$. Step 5 Stir the contents of the beaker containing the yeast suspension with the glass rod. Step 6 Add $$\(5.0 \mathrm{~cm}^{3}\)$$ of the yeast suspension to each of the test-tubes labelled $$\(0.0 \%, 0.5 \%\)$$ and $$\(1.0 \%\)$$. Step 7 Put all three test-tubes into a water-bath at $$\(40^{\circ} \mathrm{C}\)$$. Step 8 Start the stop-clock and wait for three minutes. Step 9 After three minutes, remove the test-tubes from the water-bath and place them in a test-tube rack. Step 10 Use a pipette to add one drop of methylene blue dye to each of the test-tubes. Carefully mix the contents of each test-tube with the glass rod. Step 11 Use a second pipette to slowly add a layer of oil to each of the test-tubes. The layer of oil will float on top of the yeast suspension and methylene blue mixture, as shown in Fig. 1.1. Fig. 1.1 Step 12 Put the test-tubes back into the water-bath and restart the stop-clock. Step 13 Measure the time taken for the blue colour in each of the test-tubes to disappear. Record the time taken in seconds for each test-tube. The student stopped timing if the blue colour had not disappeared after 10 minutes. They recorded this result as $$\(> 600\)$$ in their table. The stop-clocks from step 13 are shown in Fig. 1.2. $$\(0.0 \%\)$$ $$\(0.5 \%\)$$ $$\(1.0 \%\)$$ Fig. 1.2 A student investigated the effect of temperature on the rate of respiration in yeast at $$\(25^{\circ} \mathrm{C}\)$$ and $$\(35^{\circ} \mathrm{C}\)$$. In one experiment, the student measured the volume of carbon dioxide produced by the yeast every 5 minutes for a total of 30 minutes. (i) Describe suitable apparatus that could be used to collect and measure the volume of carbon dioxide produced. ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. The student did three experiments at each temperature. They used the results to calculate the mean volume of carbon dioxide produced. Part of the student's results table for the experiments at $$\(35^{\circ} \mathrm{C}\)$$ is shown in Table 1.1. Table 1.1 (ii) The student decided that the result of one of the experiments shown in Table 1.1 was anomalous. State what is meant by an anomalous result. ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (iii) Describe how the student calculated the mean volume of carbon dioxide produced shown in Table 1.1. ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. The results of the whole investigation about the effect of temperature on the rate of respiration in yeast at $$\(25^{\circ} \mathrm{C}\)$$ and $$\(35^{\circ} \mathrm{C}\)$$ are shown in Table 1.2. Table 1.2 (iv) Using the data in Table 1.2, compare the mean volumes of carbon dioxide produced at $$\(25^{\circ} \mathrm{C}\)$$ and $$\(35^{\circ} \mathrm{C}\)$$. ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ....................................................................................................................................... . ................................................................................................................................. (v) Plot a line graph on the grid of mean volume of carbon dioxide produced against time, using all of the data in Table 1.2. You will need to plot the data for each temperature as separate lines on your graph. Include a suitable key. (vi) Estimate the time taken to produce $$\(3.0 \mathrm{~cm}^{3}\)$$ of carbon dioxide at $$\(35^{\circ} \mathrm{C}\)$$. Show on the graph how you obtained your estimate. .............................................. minutes

Answer:

Knowledge points:

Solution: