SGSS Pure Biology Prelim 2024 Paper 1 & Paper 2 Answer

1 Answer Scheme for Sec 4E Biology Prelims P1 & P2 2024, St Gabriel’s Secondary School Paper 1 1 2 3 4 5 6 7 8 9 10 A D C D A B B B B D 11 12 13 14 15 16 17 18 19 20 B D C B A D A C B A 21 22 23 24 25 26 27 28 29 30 C C A D B A B C C B 31 32 33 34 35 36 37 38 39 40 D A C A D B C A C D A: 10 B: 11 C: 10 D: 9 Paper 2 Section A No. Answer Remarks 1 (a) • Between 650 and 900 cells per ml 1 1 (b) • [D1] From the 2nd to the 4th hour, the concentration of Campylobacter protein decreased from 800 cells per ml to about 220 cells per ml, by about 580 cells per ml • [D2a] From the 2nd to the 3rd hour, the concentration of Campylobacter protein decreased steeply from 800 cells per ml to about 420 cells per ml, by about 380 cells per ml • [D2b] From the 3nd to the 4th hour, the concentration of Campylobacter protein decreased less steeply from 420 cells per ml to about 220 cells per ml, by about 200 cells per ml • [E1] Antibiotics kill / inhibit bacteria growth by interfering with bacterial growth & metabolic activities, • [E2] such as inhibiting cell wall synthesis / cell membrane function / protein synthesis in ribosomes / enzyme action in cytoplasm hence concentration of Campylobacter protein decreased • [E3] Time is needed for digestion of coating / absorption / transport to area of effect, hence takes 2-4 hours for effect to show (max 4) 4

2 1 (c) Any 2: • Cell wall • Cell membrane • (free) ribosome • flagellum • circular DNA • plasmid R DNA / genetic material 2 1 (d)i • Yes, Infectious diseases can be spread from person to person • Campylobacter spreads by contaminated food / ORA 2 1 (d)ii • A vaccine contains an agent that resembles Campylobacter • White blood cells binds to antigens on vaccine • Some white blood cells remain in the blood stream for a long time as memory cells. • In the future, when the Campylobacter enters the body, memory cells recognise the pathogen • produce the antibodies to destroy it (max 3) 3

3 2 ( a ) • Wilting occurs when rate of water loss by transpiration exceeds rate of water gained from roots • Thin / small leaves reduces surface area to volume ratio • Less water loss by transpiration • Reduces chances of rate of water loss by transpiration exceeding rate of water gained from roots / OWTTE 2 2 (b) • Correct xylem label (lignified vessels) • Correct phloem label (non-lignified vessels in the core) 2 2 (c) • M: oxygen; photosynthesis • P: carbon dioxide; respiration 2 2 (d) • active transport require energy from aerobic respiration. • Root is mostly submerge in water, where there is low concentration / level of dissolved oxygen in water available for aerobic respiration. 2

4 3a • Blocked vessel: Coronary artery • Vessel A: Aorta 2 3b • less oxygen and glucose delivered to heart muscles leads to reduced rate of aerobic respiration • Heart muscle cells die leading to heart a