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Secondary 4 Pure Biology Practice Paper 5
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TuitionGoWhere Practice Paper - Pure Biology Secondary 4
Answer Key and Marking Scheme
Version: 5 of 5
Subject: Pure Biology
Level: Secondary 4
Section A: Multiple Choice Questions (10 Marks)
| Q | Answer | Marks |
|---|---|---|
| 1 | D | 1 |
| 2 | B | 1 |
| 3 | B | 1 |
| 4 | B | 1 |
| 5 | C | 1 |
| 6 | B | 1 |
| 7 | C | 1 |
| 8 | C | 1 |
| 9 | C | 1 |
| 10 | B | 1 |
Total Section A: 10 Marks
Section B: Structured Questions (40 Marks)
11.
(a) Golgi apparatus / Golgi body [1]
(b) To modify, sort, and package proteins for secretion / To form lysosomes [1]
(c) Liver cells are metabolically active / perform many reactions (e.g., detoxification, glycogen synthesis) [1]. These processes require energy [1]. Mitochondria are the site of aerobic respiration which releases energy [1]. (Max 2 marks)
(d) Double helix structure [1]. Made of two strands / polynucleotides [1]. Held together by complementary base pairs (A-T, C-G) / hydrogen bonds between bases [1].
12.
(a) pH 2 [1]
(b) Stomach [1]. The stomach contains hydrochloric acid which creates an acidic environment (low pH) [1].
(c) The enzyme denatures [1]. The hydrogen bonds holding the tertiary structure break [1]. The shape of the active site changes [1]. The substrate no longer fits the active site / no enzyme-substrate complexes form [1]. (Max 3 marks)
13.
(a) 1 / 60 = 0.017 (or 0.0167) [1]
(b) The rate of reaction increases [1]. As temperature increases, kinetic energy of molecules increases, leading to more frequent and successful collisions between enzyme and substrate [1].
(c) The high temperature (60°C) caused the enzyme to denature [1]. The active site changed shape [1]. Starch could not bind to the active site, so no reaction occurred [1].
14.
(a) Palisade mesophyll [1]
(b) Cells are columnar / arranged vertically to pack many cells in a layer [1]. Contains many chloroplasts to maximize light absorption for photosynthesis [1].
(c) To allow gas exchange (entry of CO2 and exit of O2/water vapour) [1].
(d) Guard cells surround the stoma [1]. When guard cells take in water by osmosis, they become turgid and swell, causing the stoma to open [1]. When they lose water, they become flaccid and the stoma closes [1].
15.
(a)
Starch: Blue-black colour [1]
Protein: Biuret solution [1]
(b)
(i) No reducing sugars are present [1].
(ii) Hydrolyse the sample with dilute acid (e.g., HCl) by heating [1]. Neutralize the solution with alkali (e.g., sodium hydrogen carbonate) [1]. Then perform the Benedict’s test again [1].
16.
(a) Active transport [1]
(b) 1. Movement against concentration gradient (low to high) [1].
2. Use of ATP / Energy source shown [1].
(c) Absorption of glucose / ions in the small intestine / kidney tubules [1]. Allows absorption even when concentration in the lumen is lower than in the blood/cells [1]. Ensures all nutrients/ions are absorbed from the filtrate/food [1].
17.
(a) The net movement of water molecules [1] from a region of higher water potential to a region of lower water potential [1] through a partially permeable membrane [1].
(b)
(i) The vacuole expands / increases in size [1].
(ii) Plant cells have a rigid cell wall [1]. The cell wall exerts pressure (turgor pressure) that prevents the cell from bursting [1]. Animal cells lack a cell wall.
18.
(a) Carbon, Hydrogen, Oxygen, Nitrogen [1] (Sulphur is also acceptable but not required for "all")
(b) Amino acids are joined together by condensation reactions [1]. A peptide bond is formed between the amino group of one amino acid and the carboxyl group of another [1]. This forms a polypeptide chain which folds into a specific 3D shape [1].
(c) Any two from:
- Structural components (e.g., muscle fibres, hair, nails)
- Transport (e.g., haemoglobin)
- Defense (e.g., antibodies)
- Hormones (e.g., insulin)
[2]
19.
(a) Glucose molecules are small [1]. They can pass through the pores of the dialysis tubing by diffusion [1]. Starch molecules are large / macromolecules [1]. They are too large to pass through the pores of the dialysis tubing [1].
(b) Increase the temperature / Stir the water in the beaker / Increase the surface area of the tubing [1].
20.
(a) Both involve the movement of molecules / substances across a membrane [1].
(b)
- Diffusion does not require energy (passive); Active transport requires energy (ATP) [2].
- Diffusion moves substances down the concentration gradient (high to low); Active transport moves substances against the concentration gradient (low to high) [2].
Total Section B: 40 Marks
Grand Total: 50 Marks