2024 TJC H2 Bio P4 QP

1 [TURN OVER TEMASEK JUNIOR COLLEGE 2022 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CENTRE NUMBER S INDEX NUMBER BIOLOGY 9744/04 Paper 4 Practical 28 August 2024 2 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your name, CG, Centre number, index number on all the work you hand in. Give details of the practical shift and laboratory, where appropriate, in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. This document consists of 18 printed pages and 2 blank pages. Shift Laboratory For Examiner’s Use 1 /29 2 /10 3 /16 Total /55 Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your work or if you do no u s e appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of eac h question or part question.

2 Answer all questions. 1 You are provided with a solution, labelled E, containing an enzyme which coagulates (clots) milk. Calcium ions are required for this coagulation. You are required to: • carry out a trial test to think about sources of error • investigate the effect of substrate concentration on this en zyme-catalysed coagulation. When a mixture of milk, calcium chloride solution and E is gently rotated in a boiling tube the coagulation goes through the stages shown in Fig. 1.1. Stage 4 is the end-point of the enzyme-catalysed coagulation as shown in Fig. 1.1. Fig. 1.1 You are provided with:  20% calcium chloride solution C, in a container labelled C  1% enzyme solution E, in a container labelled E  M i l k M, in a container labelled M  distilled water W, in a container labelled W. Both calcium chloride solution C and renin solution E are irrit ants. Suitable eye protection should be worn. If C or E comes into contact with your skin, wa sh off immediately under a tap. stage 1 stage 2 stage 3 near the end point stage 4 end point film of milk flows / drains back into milk quickly film of milk drains slowly and sticks to inside of boiling tube small spots / clots stick to inside of boiling tube as film of milk drains back all the milk has coagulated

3 [TURN OVER You are required to carry out a trial test (step 1 to step 16) before you start your investigation. Read step 1 to step 16 before proceeding. Proceed as follows. 1 You are provided with a beaker labelled water-bath. Use the hot and cold water to set up a water-bath in this beaker. The starting temperature of the water-bath should be between 35 °C and 40 °C. You will not need to maintain this temperature during steps 2 to 15. 2 Put 10.0 cm3 of M into a boiling tube. 3 Repeat step 2 so that you have two boiling tubes containing M. 4 Put 1.0 cm 3 of C into each boiling tube. 5 Gently shake each of the boiling tubes to mix M and C. 6 Take the temperature of the water-bath and record this temperature in (a)(ii) on page 4. 7 Put the boiling tubes into the water-bath and leave for at least 3 minutes. (a) (i) Explain why the boiling tubes are left in the water-bath for at least 3 minutes in step 7. ……………………………………………………………………………………………………… …………………………………………………………………………………………………... [1] 8 Remove one of the boiling tubes from the water-bath. The process of coagulation will start when E is added to the boiling tube. 9 Put 1.0 cm3 of E into the boiling tube, so that it runs down the side of the boiling tube and forms a layer on the surface of the mixture, as shown in Fig. 1.2. Fig. 1.2 boiling tube held at an angle

4 10 Gently shake the boiling tube to mix the solutions and start timing. 11 Hold the boiling tube over a piece of black card on the table as shown in Fig. 1.3. 12 Gently rotate the boiling tube to form a film of milk on the inside of the boiling tube. Fig. 1.3 13 Observe the film until the end-point is reached (stage 4 in Fig. 1.1). Ignore any small bubbles on the inside of the boiling tube. Stop timing. 14 Record in (a)(iii) the time taken to reach the end-point. If the end-point has not been reached in 3 minutes, stop the experiment and record ‘more than 180’. 15 Repeat step 8 to step 14 with the other boiling tube in the water-bath. 16 Take the temperature of the wate r-bath when the final boiling t ube has been removed and record this in (a)(ii). (ii) Temperature may be a source of error in this investigation. State the temperatures of the water-bath. temperature of water-bath taken in step 6 ............................................. °C temperature of water-bath taken in step 16 ........................................... °C Explain whether the temperature of the water-bath is a signific ant source of error in this investigation. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………….. [1] boiling tube held at an angle

5 [TURN OVER (iii) Record your results in an appropriate table. [3] (iv) A significant source of error for this investigation is decidin g when the end-point is reached. Suggest one advantage of carrying out this trial test before investigating the effect of substrate concentration on this enzyme-catalysed reaction. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …………………………………………………………………………………………………... [1] (v) Complete Table 1.1 by stating:  t w o other possible sources of error that may have affected your results  an improvement to reduce the effect of each error. Table 1.1 error improvement 1. 2. [4]

6 (vi) You are required to make up a final volume of 10.0 cm3 of five different concentrations of calcium chloride solution by proportional dilution. These must include 20% calcium chloride and 0% calcium chloride solutions. Show, in a table, how you will make up the calcium chloride sol ution using the 20% calcium chloride solution, C, and distilled water, W. [3] 17 Prepare all the concentrations of calcium chloride solution as shown in your table in (a)(vi). 18 Adjust the temperature of the water-bath so that it is between 35 °C and 40 °C. You will not need to maintain this temperature during step 19 to step 24. 19 Put 1.0 cm 3 of 20% calcium chloride, C into a boiling tube. 20 Put 10.0 cm3 of M into the same boiling tube. 21 Repeat step 19 with each of the other concentrations of calcium chloride solutions that you have prepared. 22 Gently shake each of the boiling tubes to mix the milk and C. 23 Put the boiling tubes in the water-bath and leave for at least 3 minutes. While you are waiting read step 8 to step 13. 24 After 3 minutes remove one of the boiling tubes from the water- bath. Add 1.0 cm 3 of E as in step 9, then repeat step 10 to step 13 and record in (a)(vii) the time taken to reach the end- point. 25 Repeat step 24 with each of the other boiling tubes.

7 [TURN OVER (vii) Record your results in an appropriate table. [4] (viii) Describe a control that could be carried out as part of your investigation ……………………………………………………………………………………………………… ………………………………………………………………………………………………….. [1]

8 (b) In a different investigation, a student studied the effect of t