Biology 0610/51 May/June 2022: question paper and mark scheme

Question

Rice contains starch. Amylase is an enzyme that catalyses the breakdown of starch to form reducing sugars. You are going to investigate the effect of amylase on cooked rice. Read all the instructions but DO NOT CARRY THEM OUT until you have drawn a table for your results in the space provided in 1(a)(i). You should use the safety equipment provided while you are carrying out the practical work. Step 1 Label one empty test-tube W10 and label the other empty test-tube A10. Step 2 Put the test-tubes in the empty beaker labelled 80 °C water-bath. Step 3 Label one of the large test-tubes containing rice W and the other large test-tube containing rice A. Step 4 Put both large test-tubes containing rice in the empty beaker labelled 40 °C water-bath. Step 5 Raise your hand when you are ready for warm water to be added to the 40 °C water-bath. Step 6 Use the measuring cylinder to add 20 cm3 of distilled water to the rice in the test-tube labelled W. Step 7 Use the measuring cylinder to add 20 cm3 of amylase solution to the rice in the test- tube labelled A. Step 8 Start the stop-clock and leave the test-tubes of rice in the 40 °C water-bath for 10 minutes. While you are waiting, carry out step 9. Step 9 Use the syringe to add 2 cm3 of Benedict’s solution to each of the empty test-tubes, W10 and A10. Put the test-tubes back in the empty beaker labelled 80 °C water-bath. Step 10 After 10 minutes (step 8), put the stopper into test-tube W and invert the test-tube three times. Remove the stopper. Step 11 Use a clean pipette to remove 2 cm3 of the liquid surrounding the rice in test-tube W. Put the 2 cm3 of liquid into test-tube W10. Put test-tube W10 back into the beaker labelled 80 °C water-bath. Step 12 Repeat steps 10 and 11 with test-tubes A and A10. Step 13 Raise your hand when you are ready for hot water to be added to the beaker labelled 80 °C water-bath. Step 14 Leave test-tubes W10 and A10 in the 80 °C water-bath for 10 minutes. While you are waiting continue with the other questions. Step 15 After 10 minutes, record the colour of the liquid in test-tubes W10 and A10 in the table you have prepared in 1(a)(i). (a) (i) Prepare a table to record your results. [3] (ii) State a conclusion for your results. …… [1] (iii) State one variable that was kept constant in this investigation. …… [1] (iv) State the purpose of adding distilled water to the test-tube of cooked rice labelled W. …… [1] (v) It was important that step 6 was carried out before step 7. Predict the effect on the results if step 7 was carried out before step 6. …… [1] (vi) The temperature of the 40 °C water-bath will decrease during the investigation. State one piece of equipment that could be used to maintain the temperature at 40 °C. …… [1] (b) State how you could show that cooked rice contains starch. …… [2] (c) Some students investigated the effect of temperature on the rate of amylase activity. They measured the mass of reducing sugars produced in five minutes, at different temperatures. The results of this investigation are shown in Fig. 1.1. 60 50 40 mass of reducing sugars produced in five 30 minutes / mg 20 10 0 0 10 20 30 40 50 60 temperature / °C Fig. 1.1 (i) Describe the effect of temperature on the activity of amylase shown in the graph in Fig. 1.1. …… [2] (ii) Use the graph to estimate the rate of amylase activity, in mg per minute, at a temperature of 42 °C. Space for working. …… mg per minute [2] (iii) The students wanted to obtain a more accurate value for the temperature at which amylase works best. Suggest further investigative work that the students should carry out. …… [2] (d) Plan an investigation to determine the effect of pH on the activity of amylase. …… [6] [Total: 22]

Question

Fig. 2.1 is a photomicrograph of a section through part of a marram grass leaf, Ammophila arenaria. Fig. 2.1 (a) (i) Draw a large diagram of the section of marram grass leaf shown in Fig. 2.1. Do not draw individual cells. [4] (ii) Fig. 2.2 shows a cross-section of a whole marram grass leaf. Q P magnification ×120 Fig. 2.2 Measure the length of line PQ on Fig. 2.2. length of line PQ …… mm Calculate the actual diameter of the marram grass leaf using the formula and your measurement. length of line PQ on Fig. 2.2 magnification = actual diameter of the marram grass leaf Give your answer to one decimal place. Space for working. …… mm [3] (b) Scientists investigated the effect of different concentrations of sodium chloride solution on the germination and growth of marram grass. Marram grass seeds were germinated in Petri dishes on filter paper which had been soaked in one of the different sodium chloride solutions. Each Petri dish contained 15 seeds and the investigation was repeated four times. After 20 days, the lengths of the seedling roots were measured with a ruler. (i) State the variable that was changed (independent variable) and the variable that was measured (dependent variable) in this investigation. independent variable …… dependent variable …… [2] (ii) State two ways the scientists designed the investigation to produce valid and reliable results. 1 …… 2 …… [2] (c) The results of the investigation described in 2(b) are shown in Table 2.1. Table 2.1 concentration of average root length sodium chloride / mm solution / g per dm3 0 33 2 22 4 19 6 13 8 2 10 1 (i) Using the information in Table 2.1, calculate the percentage decrease in the average root length when the concentration of sodium chloride was changed from 4 g per dm3 to 6 g per dm3. Give your answer to three significant figures. Space for working. …… % [3] (ii) Plot a line graph on the grid of the data in Table 2.1. [4] [Total: 18]