2024 TJC H2 Bio P4 MS

1 [TURN OVER TEMASEK JUNIOR COLLEGE 2024 JC2 PRELIMINARY EXAMINATION Higher 2 BIOLOGY 9744/04 Paper 4 Practical Answers 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, cal cium 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. 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 cm 3 of M into a boiling tube. 3 Repeat step 2 so that you have two boiling tubes containing M. 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