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Secondary 4 Pure Biology Practice Paper 1
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Questions
Secondary 4 Pure Biology Quiz - Cells Biomolecules
Name: __________________________
Class: __________________________
Date: __________________________
Score: ________ / 40
Duration: 45 minutes
Total Marks: 40
Instructions:
- Answer all questions.
- Write your answers in the spaces provided.
- The number of marks for each question or part question is given in brackets [ ].
Section A: Cell Structure and Organisation (Questions 1–5)
1. Fig. 1.1 shows a diagram of a typical animal cell as seen under an electron microscope.
(Imagine a diagram showing a nucleus, mitochondria, rough endoplasmic reticulum, and cell membrane)
(a) Identify the structure labelled A which appears as a network of membranes studded with small dots.
_________________________________________________________________________ [1]
(b) State the function of the small dots found on structure A.
_________________________________________________________________________ [1]
(c) Explain why muscle cells contain a higher number of mitochondria compared to skin cells.
_________________________________________________________________________ [2]
2. A student observes two cells under a light microscope. Cell X has a cell wall, a large central vacuole, and chloroplasts. Cell Y has no cell wall and irregular shape.
(a) Identify whether Cell X is a plant cell or an animal cell.
_________________________________________________________________________ [1]
(b) State one function of the cell wall in Cell X.
_________________________________________________________________________ [1]
(c) Explain why Cell Y does not have chloroplasts.
_________________________________________________________________________ [2]
3. Red blood cells are specialised for their function in the human body.
(a) State the main substance transported by red blood cells.
_________________________________________________________________________ [1]
(b) Describe one structural adaptation of red blood cells that helps them perform this function efficiently.
_________________________________________________________________________ [2]
4. The nucleus is often described as the "control centre" of the cell.
(a) Name the molecule found inside the nucleus that carries genetic information.
_________________________________________________________________________ [1]
(b) Explain how the nucleus controls the activities of the cell.
_________________________________________________________________________ [2]
5. Compare the structure of a typical plant cell and a typical animal cell by completing the table below.
| Feature | Plant Cell | Animal Cell |
|---|---|---|
| Cell Wall | Present | (a) _______________ [1] |
| Chloroplasts | (b) _______________ [1] | Absent |
| Vacuole | Large, permanent | (c) _______________ [1] |
Section B: Movement of Substances (Questions 6–12)
6. Define the term diffusion.
_________________________________________________________________________ [2]
7. Fig. 7.1 shows an experiment set up to demonstrate osmosis. A visking tubing bag containing concentrated sugar solution is placed in a beaker of distilled water.
(a) Define osmosis.
_________________________________________________________________________ [2]
(b) After 30 minutes, the level of liquid in the thistle funnel rises. Explain why this happens.
_________________________________________________________________________ [3]
8. A plant cell is placed in a concentrated salt solution.
(a) Name the process that causes water to leave the cell.
_________________________________________________________________________ [1]
(b) Describe the appearance of the cell after 10 minutes.
_________________________________________________________________________ [2]
(c) Explain why animal cells burst when placed in distilled water, but plant cells do not.
_________________________________________________________________________ [2]
9. Root hair cells absorb mineral ions from the soil even when the concentration of ions in the soil is lower than in the cell sap.
(a) Name the process by which these ions are absorbed.
_________________________________________________________________________ [1]
(b) State two requirements for this process to occur.
-
- ______________________________________________________________________ [2]
10. Fig. 10.1 shows the concentration of glucose in the small intestine and in the blood capillaries of a villus.
- Glucose concentration in intestine: High
- Glucose concentration in blood: Low (initially)
(a) Name the process by which glucose initially moves from the intestine into the blood.
_________________________________________________________________________ [1]
(b) Later, the concentration of glucose in the blood becomes higher than in the intestine, yet glucose continues to be absorbed. Name the process responsible for this.
_________________________________________________________________________ [1]
11. Explain the importance of a large surface area to volume ratio for cells involved in absorption, such as root hair cells.
_________________________________________________________________________ [2]
12. A student investigates the effect of surface area on the rate of diffusion using agar cubes containing phenolphthalein soaked in sodium hydroxide, placed in dilute hydrochloric acid.
(a) Predict which cube will change colour completely first: a 1cm³ cube or a 2cm³ cube.
_________________________________________________________________________ [1]
(b) Explain your prediction.
_________________________________________________________________________ [2]
Section C: Biological Molecules and Enzymes (Questions 13–20)
13. Complete the table below regarding biological molecules.
| Molecule | Elements Present | Basic Unit (Monomer) | Food Test Reagent |
|---|---|---|---|
| Starch | C, H, O | (a) ___________ [1] | Iodine Solution |
| Protein | C, H, O, N | Amino Acid | (b) ___________ [1] |
| Fat | C, H, O | (c) ___________ [1] | Ethanol + Water |
14. Describe how you would test a food sample for the presence of reducing sugars. Include the reagent used, the method, and the positive result.
_________________________________________________________________________ [3]
15. Enzymes are biological catalysts.
(a) Define the term catalyst.
_________________________________________________________________________ [1]
(b) Explain the "lock and key" hypothesis of enzyme action.
_________________________________________________________________________ [3]
16. Fig. 16.1 shows the effect of temperature on the rate of reaction of an enzyme.
(Imagine a graph showing rate increasing up to 40°C, then dropping sharply to zero at 60°C)
(a) Explain why the rate of reaction increases between 10°C and 40°C.
_________________________________________________________________________ [2]
(b) Explain why the rate of reaction drops to zero at 60°C.
_________________________________________________________________________ [3]
17. Pepsin is an enzyme found in the stomach that breaks down proteins.
(a) State the optimum pH for pepsin.
_________________________________________________________________________ [1]
(b) Explain what would happen to the activity of pepsin if it were moved to the small intestine (pH 8).
_________________________________________________________________________ [2]
18. A student investigates the effect of substrate concentration on enzyme activity.
(a) Describe the relationship between substrate concentration and the rate of reaction when substrate concentration is low.
_________________________________________________________________________ [1]
(b) Explain why the rate of reaction levels off (plateaus) at high substrate concentrations.
_________________________________________________________________________ [2]
19. Why are enzymes specific to particular substrates?
_________________________________________________________________________ [2]
20. Explain why enzymes are essential for life processes in living organisms.
_________________________________________________________________________ [2]
END OF QUIZ
Answers
Secondary 4 Pure Biology Quiz - Cells Biomolecules (Answer Key)
Total Marks: 40
Section A: Cell Structure and Organisation
1.
(a) Rough Endoplasmic Reticulum (Rough ER) [1]
(b) Protein synthesis [1]
(c) Muscle cells require more energy for contraction [1]. Mitochondria are the site of aerobic respiration which releases energy [1].
2.
(a) Plant cell [1]
(b) Provides structural support / Maintains cell shape / Prevents bursting under turgor pressure [1]
(c) Cell Y is an animal cell [1]. Animal cells do not perform photosynthesis, so they do not need chloroplasts [1].
3.
(a) Oxygen [1]
(b) Biconcave shape increases surface area for faster diffusion of oxygen [1] OR No nucleus allows more space for haemoglobin to carry oxygen [1]. (Accept either)
4.
(a) DNA (Deoxyribonucleic acid) [1]
(b) The nucleus contains genes/DNA which code for proteins [1]. These proteins (enzymes) control chemical reactions and cell activities [1].
5.
(a) Absent [1]
(b) Present [1]
(c) Small, temporary / Many small vacuoles [1]
Section B: Movement of Substances
6.
The net movement of particles [1] from a region of higher concentration to a region of lower concentration [1] (down a concentration gradient).
7.
(a) The net movement of water molecules [1] from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) [1] through a partially permeable membrane.
(b) The sugar solution has a lower water potential than the distilled water [1]. Water molecules move by osmosis [1] from the beaker into the visking tubing [1], causing the volume/level to rise.
8.
(a) Osmosis [1]
(b) The cytoplasm shrinks / pulls away from the cell wall [1]. The cell becomes plasmolysed [1].
(c) Animal cells lack a cell wall [1]. Water enters by osmosis, causing the cell to swell and burst (lyse) [1]. Plant cells have a strong cell wall that prevents bursting [1]. (Note: Question asks why plant cells do not burst, so 1 mark for cell wall presence is sufficient if linked to prevention of bursting).
9.
(a) Active Transport [1]
(b) 1. Energy (ATP) from respiration [1]
2. Carrier proteins [1]
10.
(a) Diffusion [1]
(b) Active Transport [1]
11.
A large surface area allows for a faster rate of absorption/diffusion [1]. It provides more space for carrier proteins/channels or contact with the soil/water [1].
12.
(a) The 1cm³ cube [1]
(b) It has a larger surface area to volume ratio [1]. This allows the acid to diffuse into the centre of the cube faster [1].
Section C: Biological Molecules and Enzymes
13.
(a) Glucose [1]
(b) Biuret Solution [1]
(c) Fatty acids and Glycerol [1] (Both must be correct)
14.
Add Benedict’s solution to the food sample [1]. Heat the mixture in a water bath (boil) [1]. A positive result is a colour change from blue to green/yellow/orange/brick-red precipitate [1].
15.
(a) A substance that speeds up the rate of a chemical reaction [1] without being used up/changed in the process.
(b) The enzyme has an active site with a specific shape [1]. The substrate has a complementary shape [1]. The substrate fits into the active site to form an enzyme-substrate complex [1].
16.
(a) As temperature increases, kinetic energy of enzyme and substrate molecules increases [1]. This leads to more frequent collisions between enzyme and substrate [1].
(b) High temperature breaks the bonds holding the enzyme structure together [1]. The enzyme denatures [1]. The shape of the active site changes, so the substrate no longer fits [1].
17.
(a) pH 2 (or acidic pH / pH 1-3) [1]
(b) The enzyme will denature [1] because the pH is too high/alkaline for pepsin, changing the shape of the active site [1].
18.
(a) The rate of reaction increases [1].
(b) All active sites of the enzyme molecules are occupied/saturated [1]. Adding more substrate cannot increase the rate further as there are no free active sites [1].
19.
Enzymes have a specific active site shape [1]. Only substrates with a complementary shape can fit into the active site [1].
20.
Metabolic reactions in the body would be too slow to sustain life without enzymes [1]. Enzymes lower the activation energy required for reactions to occur at body temperature [1].