Biology 0610/52 May/June 2021: question paper and mark scheme

Question

Catalase is an enzyme found in living cells. It catalyses the break-down of hydrogen peroxide to form water and oxygen. You are going to investigate the effect of catalase concentration on the rate of oxygen production. You have been provided with a celery extract which contains catalase. 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)(ii). You should use the safety equipment provided while you are carrying out the practical work. Step 1 Label five test-tubes A, B, C, D and E. Put the test-tubes into the test-tube rack. Step 2 Use a measuring cylinder to pour 10 cm3 of celery extract into test-tube A. Step 3 Use the measuring cylinder to transfer 5 cm3 of celery extract from test-tube A to test- tube B. Use the measuring cylinder to add 5 cm3 of distilled water to test-tube B. Place a stopper in test-tube B and shake it three times. Step 4 Remove the stopper. Use the measuring cylinder to transfer 5 cm3 of the liquid in test- tube B to test-tube C. Use the measuring cylinder to add 5 cm3 of distilled water to test-tube C. Place a stopper in test-tube C and shake it three times. Step 5 Remove the stopper. Use the measuring cylinder to transfer 5 cm3 of the liquid in test- tube C to test-tube D. Use the measuring cylinder to add 5 cm3 of distilled water to test-tube D. Place a stopper in test-tube D and shake it three times. Step 6 Remove the stopper. Use the measuring cylinder to transfer 5 cm3 of the liquid in test- tube D to test-tube E. Use the measuring cylinder to add 5 cm3 of distilled water to test-tube E. Place a stopper in test-tube E and shake it three times. Remove the stopper. (a) (i) Table 1.1 shows the concentration of the celery extract in test-tubes A to E. Table 1.1 percentage test-tube concentration of celery extract A 100.00 B 50.00 C D 12.50 E 6.25 Complete Table 1.1 by calculating and writing in the percentage concentration of celery extract in test-tube C. [1] Step 7 Pour a small amount of the celery extract from test-tube A onto the watch glass, as shown in Fig. 1.1. watch glass celery extract Fig. 1.1 Step 8 Use the forceps to place one of the paper discs into the celery extract in the watch glass. Step 9 Use the ruler to measure 2 cm from the top (open end) of the remaining unlabelled test-tube. Mark this distance by drawing a line on the test-tube with the marker pen. Step 10 Use the forceps to remove the paper disc from the watch glass. Place the paper disc into the test-tube you prepared in step 9. Push the paper disc to the bottom of the test-tube with the glass rod. Step 11 Carefully pour hydrogen peroxide solution into the test-tube until it reaches the line you marked on the test-tube in step 9. Immediately start the stop-clock and observe the paper disc rising. Stop the stop-clock when the paper disc reaches the surface of the hydrogen peroxide solution. Record the time taken for the disc to rise, in your table in 1(a)(ii). Record the time in seconds. If the paper disc has not reached the surface of the hydrogen peroxide solution after three minutes, stop the stop-clock and record the time as >180 in your table. Step 12 Pour the hydrogen peroxide solution and paper disc into the beaker labelled waste. Empty the contents of the watch glass into the waste beaker. Wipe the watch glass with a paper towel. Step 13 Repeat steps 7 to 12 using the celery extract in test-tubes B, C, D and E. (ii) Prepare a table to record your results. [4] (iii) State a conclusion for this investigation. …… [1] (iv) Identify the variable that you have changed (independent variable) and the variable you have measured (dependent variable) in this investigation. independent variable …… dependent variable …… [2] (b) (i) The oxygen gas produced by the reaction forms bubbles on the paper disc. The bubbles cause the disc to rise to the top of the hydrogen peroxide solution. The time taken for the disc to rise can be used to calculate the rate of the reaction. Explain how you could calculate the rate at which the disc rises. …… [2] (ii) Identify one source of error in step 4 and one source of error in step 11. error in step 4 …… error in step 11 …… [2] (c) Sodium chloride affects the activity of the enzyme catalase. This enzyme catalyses the break-down of hydrogen peroxide to release water and oxygen gas. catalase 2H2O2 2H2O + O2 hydrogen peroxide water oxygen Plan an experiment to determine the effect of sodium chloride concentration on the volume of oxygen gas produced during this reaction. …… [6] (d) The enzyme catalase is a protein. State the test for protein and state the result of a positive test. test …… positive test result …… [2] [Total: 20]

Question

(a) The photograph in Fig. 2.1 shows a leaf from a European holly tree (Ilex aquifolium). prickle Q P Fig. 2.1 (i) Draw a large diagram of the holly leaf shown in Fig. 2.1. Do not label your drawing. [4] (ii) The line PQ on Fig. 2.1 shows the length of the leaf. Measure the length of line PQ on Fig. 2.1. Include the unit. length of line PQ …… Draw a line on your drawing in the same position as line PQ in Fig. 2.1. Measure the length of the line you have drawn. Include the unit. length of the line on your drawing …… Calculate the magnification of your drawing using your measurements and the formula. length of the line on your drawing magnification = length of line PQ in Fig. 2.1 Space for working. [3] (b) Students investigated the relationship between the number of prickles on holly leaves and the height of the leaves above the ground. • The students collected leaves from a total of five holly trees. • The students took leaves from seven different heights on each holly tree. • They collected 10 leaves from each height on each tree. • They counted the number of prickles on each of the holly leaves and calculated the average number of prickles per leaf at each height. The results of the investigation are shown in Table 2.1. Table 2.1 height above ground on average number of each holly tree / m prickles per leaf 0.5 18 1.0 14 1.5 13 2.0 3.0 8 4.0 3 5.0 1 (i) The students counted a total of 614 prickles on the leaves collected at a height of 2.0 metres. Calculate the total number of leaves collected at 2.0 metres above ground …… Then calculate the average number of prickles per leaf. Give your answer to the nearest whole number. Space for working. [3] (ii) State two ways the students ensured that they collected a representative sample of leaves. 1 …… 2 …… [2] (iii) Plot a line graph on the grid to show the data in Table 2.1. Include a line of best fit. [4] (c) Fig. 2.2 shows another holly leaf. Fig. 2.2 Count and record the number of prickles on the leaf shown in Fig. 2.2. Use the information in Table 2.1 or your graph in 2(b)(iii) to estimate the height on the tree from which this holly leaf was collected. number of prickles …… estimated height on the holly tree …… m [2] (d) Leaves contain starch. State the solution used to test for starch and give the result of a positive test. solution …… positive test result …… [2] [Total: 20]