YCKSS Pure Biology Prelim 2024 Paper 1 & Paper 2 Answer

Secondary 4 Biology 2024 Preliminary Examination Suggested Answer 1 B 6 B 11 B 16 D 21 C 26 A 31 C 36 B 2 D 7 C 12 C 17 C 22 A 27 B 32 C 37 A 3 B 8 A 13 D 18 A 23 A 28 C 33 D 38 B 4 A 9 D 14 B 19 C 24 D 29 D 34 C 39 B 5 D 10 B 15 A 20 C 25 B 30 C 35 B 40 C

1(a)(i) root hair cell + long and narrow protrusion 1 1(a)(ii) 1 soil water has a higher water potential than the cell sap of root hair cell / cell A 2 hence, water molecules moved from soil water to the cell sap of root hair cell / cell A via osmosis through a partially permeable membrane 3 cell sap of root hair cell now has a higher water potential than cell sap of cortical cells leading to water molecules moving into the cell sap of cortical cells 4 this process continues until water molecules reaches the xylem vessel 3 1(b)(i) still air: graph C moving air: graph B 1 1(b)(ii) 1 In the presence of moving air, there is a greater mass of water los t from 0 to 30 minutes, where the greatest mass of water lost is (6.1 – 2.1 =) 4.0 g at 30 min 2 Moving air removes the layer of water vapour immediately outside the leaves, reducing / lowering the concentration gradient of water vapour between the intercellular air spaces and the atmospheric air compared to the plant in still air 3 Hence, there is a higher net rate of water vapour diffusing out of the intercellular air spaces (through the stomata) to the atmospheric air in the plant exposed to moving air 3 1(c)(i) 252 1 1(c)(ii) any three from: 1 (carbon dioxide /  14C) enters (leaf), through stoma(ta) / by diffusion and diffuses into the chloroplast 2 photosynthesis occurs and radioactive carbon dioxide is converted to glucose in the presence of light energy and chlorophyll 3 excess glucose is then converted to sucrose for transportation 3 [Total: 12] 2(a) D 1 2(b)(i) 1 test-tube 3 contained bile but test-tube 2 did not. Bile emulsifies large fat droplets into smaller fat droplets 2 increases surface area to volume ratio of fats for a faster rate of digestion by lipase into fatty acids and glycerol in test-tube 3 than 2 3 since fatty acids are acidic, hence, pH in test -tube 3 decreases faster / at an earlier time than test-tube 2 3 2(b)(ii) any one from: 1 shows that bile, does not (chemically) digest fats / does not make solution acidic ; 2 shows that, lipase / enzyme, is required (for breakdown of fats into fatty acids and glycerol) 1

2(c)(i) line drawn showing that decrease after optimum is steeper than increase ; 1 line does not have to start at the origin or end at the x-axis label line to point where line meets the x -axis and label indicating that all the lipase is denatured / AW ; 2 line must meet the x-axis 2 [Total: 7] 3(a) 1 light is refracted / bent by cornea 2 ciliary muscles / body contract + suspensory ligaments become slack 3 lens becomes more convex + light rays refracted / bent (more) by lens formed on retina 3 3(b) len