PLMGS S4Exp 5NA Sc Bio Prelim_P4_2025_Answer

1 Preliminary Examination 2025 (Term 3) Secondary 4 Express & 5 Normal Academic Science Biology 5088 Qn Answer Marks Remarks Learning Outcome 1(a) (i) (ii) mark awarded only if structure is in a plausible position nucleus / mitochondrion / vacuole (shown in both cells); Ignore: cytoplasm Any 2 from: chloroplast / cell wall / one large central vacuole in plant cell + many small vacuoles in animal cell; 1 1 nucleus: large, round mitochondrion: bean-shaped ignore: size of organelles cell wall: even thickness around cell membrane 1 Cell (c) compare the structure of typical animal and plant cells vacuoles vacuole

2 1(b) (i) (some plant tissues) carry out photosynthesis + produces / manufactures glucose [or] excess glucose is converted to starch for storage / starch storage [or] presence of cellulose in the cell wall; 1 (ii) 1. liver / muscles; 2. storage of glycogen; 2 (iii) Any 1 from (proteins): 1. to synthesize new cytoplasm; 2. to build and repair tissues; 3. to synthesize enzymes; 4. to synthesize hormones; ignore: to synthesize antibodies (antibodies are only found in animal cells, not in plant tissues) Any 1 from (fats) 5. energy storage; 6. component of cell membrane; 7. to reduce water loss (e.g: oily substance found on the skin surface / waxy layer on the epidermis of leaves) ignore: insulation (less relevant in plant tissues) max: 2 MP5: seeds contain fats 3 Biological Molecules: (a) state the main roles of carbohydrates, fats and proteins in living organisms. [Total: 7 marks]

3 2(a) Any 2 from: 1. net movement of water molecules; 2. from a region of high water potential to a region of low water potential 3. across a partially permeable membrane; 2 2 Movement of Substances (b) define osmosis, investigate and describe the effects of osmosis on plant and animal tissues 2(b) 1. (water molecules) move by osmosis; 2. from large intestine, higher water potential + to blood plasma, lower water potentia l + down the water potential gradient; 3. large intestine membrane is a partially permeable membrane; 3 2(c) (i) 2 1 mark for each correct line; 2(c) (ii) as surface area to volume ratio decreases + time taken for diffusion increases + rate of diffusion decreases; 1

4 2(d) Any 2 from: 1. many / numerous alveoli + to increase surface area; 2. surrounded by many blood capillaries + to maintain diffusion gradient + to remove absorbed materials; 3. one-cell thick alveolar wall and blood capillary wall + to shorten the diffusion distance; max: 2 6 Respiration in humans (b) explain how the structure of an alveolus is suited for its function of gaseous exchange [Total: 10 marks]

5 3(a) nucleus / chromosomes; 1 3(b) (i) 1. Dd + Dd; 2. correctly shown gametes; 3. correctly shown gamete linkage + offspring genotype and offspring phenotype; 3 12 Inheritance (d)