2022 J2 ASRJC H2 Biology Prelims Paper 3 (Ans)

ASRJC BIOLOGY DEPT 9744//2022/J2PRELIM/P3 [Turn over H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 ANSWERS 2022 JC2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS INDEX NUMBER BIOLOGY 9744/03 PAPER 3 LONG STRUCTURED AND FREE RESPONSE QUESTIONS Candidates answer on the Question Paper. No Additional Materials are required. 15 SEPTEMBER 2022 THURSDAY 2 HOURS READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graph Do not use paper clips, highlighters, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question 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 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. This document consists of 13 printed pages and 1 blank page For Examiner’s Use 1 / 30 2 / 10 3 / 10 4 /5 / 25 Total / 75

ASRJC BIOLOGY DEPT 9744//2022/J2PRELIM/P3 Section A Answer all the questions in this section. 1 Lactose is a disaccharide found in milk. Lactase , an enzyme found in mammals and some fungi, catalyse the breakdown of lactose. The lactase enzyme is made up of 4 identical polypeptide chains. In humans, molecules of lactase are embedded in the cell surface membrane of epithelial cells lining the small intestine. As the lactose molecules float by in the lumen, they are broken down. (a) Explain how the polypeptide chains in lactase are held together and how they interact with the cell surface membrane. How polypeptide chains are held together 1. by R group interactions such as 2 named bonds: ionic bonds, hydrogen bonds, hydrophobic interactions ( accept disulfide bonds) how they interact with the cell surface membrane 2. Part of polypeptide chain with polar/charged (acidic and basic) / hydrophilic amino acids are able to associate with polar/ charged/ hydrophilic phosphate head of phospholipids via hydrogen/ ionic/ bonds. Reject polar/ charged protein 3. Parts of polypeptide chain with non-polar/ hydrophobic amino acids associate with non-polar/ hydrophobic fatty acid tails of phospholipids via hydrophobic interactions [3]

3 ASRJC BIOLOGY DEPT