2025 TMJC H2Bio PE P2 (A)

CANDIDATE NAME CIVICS GROUP H2 BIOLOGY 9744/02 Paper 2 Structured Questions 17 September 2025 2 hours Candidates answer on the Question Paper. No additional materials are required. ______________________________________________________________________________________ This document consists of 29 printed pages and 1 blank page. TAMPINES MERIDIAN JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION SUGGESTED ANSWERS

2 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Biology Answer all questions. 1. Fig. 1.1 shows a diagram of a glycosphingolipid, a type of lipid found in the cell surface membranes of most eukaryotic organisms. Fig. 1.1 (a) Compare the structures of the glycosphingolipid and phospholipids. [2] No. feature glycosphingolipid phospholipid 1 no. of fatty acid tails / hydrocarbon chains two 2 head group sugar molecule / monosaccharide phosphate head 3 bond joining sugar / glycerol to fatty acid ether bond / glycosidic bond ester bond 4 elements present C, H, O, P C, H, O, N 5 presence of glycerol absent present (b) Suggest a role of the glycosphingolipid in the cell surface membrane. [1] • Cell-to-cell recognition / cell-to-cell adhesion / regulate membrane fluidity Accept: (precursor) to form second messenger (c) Glucocerebrosidase is a glycosidase enzyme that breaks down glycosphingolipids by removing the saccharide portion of the molecule. Another example of a glycosidase enzyme is maltase that breaks down maltose into glucose molecules. Draw an arrow in Fig. 1.1 to show which bond glucocerebrosidase hydrolyses in the glycosphingolipid. [1]

3 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Biology (d) Fig. 1.2 shows the results of an experiment conducted to investigate the activity of glucocerebrosidase at various pH levels. Fig. 1.2 Explain why there is no enzyme activity below pH 3. [3] 1. Below pH 3, charged and/or polar R -groups of amino acids in the enzyme are neutralised. 2. Ionic and hydrogen bonds (ecf from point 1) between amino acids are disrupted. 3. There is a change in 3D conformation of the enzyme, hence the active site is no longer complementary to the substrate 4. No enzyme-substrate complex can be formed to catalyse the hydrolysis of the bond. Accept: less

4 Tampines Meridian Junior College 2025 JC2 Preliminary Examination H2 Biology (e) Another experiment was conducted to investigate the effect of substrate concentration on the activity of glucocerebrosidase, with and without a chemical called isofagomine. The results are shown in Fig. 1.3. Fig. 1.3