MI 2023 H2 Biology Paper 4 ANS

Class Adm No Candidate Name: This question paper consists of 19 printed pages, including 1 blank page. [Turn over] 2023 End-of-Year Examination Pre-university 3 BIOLOGY HIGHER 2 9744/04 Paper 4 Practical 29 August 2023 Candidates answer on the Question Paper 2 hour 30 minutes READ THESE INSTRUCTIONS FIRST Do not open this booklet until you are told to do so. 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 and graphs. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. Answer all questions in the spaces provided on the Question Paper. The use of scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use 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 each question or part question. Shift Laboratory For Examiner's Use 1 /20 2 /21 3 /14 Total /55

2 9744/PU3 BIO EOY/2023 Candidates with access to microscope at the start of the paper are given the first 1 hour 15 mins to use it. Please answer question 3, within this time frame. Candidates with no access to microscope at the start of t he paper will be given access 1 hour 15 minutes after the start of the paper. You may proceed with Question 1 first. Answer all questions. Question 1 You are provided with a solution labelled E containing an enzyme which coagulates (clots) milk. Enzyme E hydrolyse peptide bonds between certain amino acids in a protein found in milk and this results in the coagulation of the milk. Calcium ions are needed for this coagulation. When a mixture of milk, calcium chloride solution and E is gently turned in a test -tube, the coagulation goes through the stages shown in Fig. 1.1. Stage 3 is the end-point of the enzyme-catalysed coagulation. Fig. 1.1 You will investigate the effect of temperature on the time taken to reach the end-point. You will test the activity of enzyme E at 30oC and other temperatures up to a maximum of 50oC. You are provided with: • 70 cm3 of 100% milk, labelled M • 20 cm3 of enzyme solution, labelled E • 20 cm3 of calcium chloride solution, labelled C If C or E comes into contact with your skin, wash off immediately under water. It is recommended that you wear suitable eye protection. (a) (i) List the temperatures that you will be using to investigate the effect of temperature on the enzyme of enzyme E. You must include 30 oC and 50oC in the range of temperatures. ……………………………………………………………………………………………………… [1] 30oC, 35oC, 40 oC, 45 oC, 50oC;

3 9744/PU3 BIO EOY/2023 [Turn over] Read steps 1 to 12. Proceeds as follows. 1 Set up a water bath at 30oC to be used later in step 5.