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Secondary 4 Pure Biology Cells Biomolecules Quiz
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Questions
Secondary 4 Pure Biology Quiz - Cells Biomolecules
Name: __________________________
Class: __________________________
Date: __________________________
Score: ________ / 45
Duration: 45 minutes
Total Marks: 45
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 [ ].
- Use a black or blue pen. Diagrams may be drawn in pencil.
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 observed two cells, Cell X and Cell Y, under a light microscope.
- Cell X has a cell wall, a large central vacuole, and chloroplasts.
- Cell Y has no cell wall, no chloroplasts, and small temporary vacuoles.
(a) Identify whether Cell X is a plant cell or an animal cell.
_________________________________________________________________________ [1]
(b) State one function of the cell wall found in Cell X.
_________________________________________________________________________ [1]
(c) Explain why Cell Y does not contain chloroplasts.
_________________________________________________________________________ [2]
3. Red blood cells are specialised for their function in the human body.
(a) State the main pigment found in red blood cells.
_________________________________________________________________________ [1]
(b) Explain how the biconcave shape of a red blood cell aids its function.
_________________________________________________________________________ [2]
(c) Mature mammalian red blood cells lack a nucleus. Explain one advantage of this absence.
_________________________________________________________________________ [2]
4. Fig. 4.1 shows a root hair cell.
(a) State the process by which water enters the root hair cell from the soil.
_________________________________________________________________________ [1]
(b) Explain how the long projection of the root hair cell increases the efficiency of water uptake.
_________________________________________________________________________ [2]
5. Compare the structural differences between a typical prokaryotic cell (e.g., bacterium) and a typical eukaryotic cell (e.g., animal cell) by completing the table below.
| Feature | Prokaryotic Cell | Eukaryotic Cell |
|---|---|---|
| Nucleus | _________________________ | _________________________ |
| Ribosomes | _________________________ | _________________________ |
| Mitochondria | _________________________ | _________________________ |
[3]
Section B: Movement of Substances (Questions 6–10)
6. Define the term diffusion.
_________________________________________________________________________ [2]
7. Fig. 7.1 shows an experiment set up to demonstrate osmosis using visking tubing (a partially permeable membrane).
- Setup A: Visking tubing filled with concentrated sugar solution, placed in distilled water.
- Setup B: Visking tubing filled with distilled water, placed in concentrated sugar solution.
(a) Predict the change in volume of the liquid inside the visking tubing for Setup A after 30 minutes.
_________________________________________________________________________ [1]
(b) Explain your answer for Setup A in terms of water potential.
_________________________________________________________________________ [3]
8. Active transport is essential for the uptake of mineral ions by root hair cells.
(a) Define active transport.
_________________________________________________________________________ [2]
(b) State two requirements for active transport to occur.
-
- _________________________________________________________________________ [2]
(c) Explain why root hair cells contain many mitochondria.
_________________________________________________________________________ [2]
9. A student placed three strips of potato tissue into three different solutions:
- Solution P: Distilled water
- Solution Q: 0.5 mol/dm³ sucrose solution
- Solution R: 1.0 mol/dm³ sucrose solution
After 1 hour, the student measured the change in length of each strip.
(a) Which solution caused the potato strip to become turgid?
_________________________________________________________________________ [1]
(b) Explain why the potato strip in Solution R became flaccid.
_________________________________________________________________________ [3]
10. Fig. 10.1 shows the concentration of potassium ions inside a root hair cell and in the surrounding soil water.
- Concentration in root hair cell: High
- Concentration in soil water: Low
(a) Name the process by which potassium ions move from the soil into the root hair cell.
_________________________________________________________________________ [1]
(b) Explain why diffusion cannot account for this movement.
_________________________________________________________________________ [2]
Section C: Biological Molecules and Enzymes (Questions 11–15)
11. Complete the table below regarding biological molecules.
| Biological Molecule | Elements Present | Building Block (Monomer) | Food Test Reagent |
|---|---|---|---|
| Starch | C, H, O | _________________________ | _________________________ |
| Protein | C, H, O, N | _________________________ | Biuret Solution |
| Fat | C, H, O | Glycerol and Fatty Acids | _________________________ |
[4]
12. Describe how you would test a food sample for the presence of reducing sugars. Include the reagent used, the procedure, and the positive result.
_________________________________________________________________________ [4]
13. Enzymes are biological catalysts.
(a) Define the term catalyst.
_________________________________________________________________________ [2]
(b) Explain the "lock and key" hypothesis of enzyme action.
_________________________________________________________________________ [4]
14. Fig. 14.1 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.
_________________________________________________________________________ [3]
(b) Explain why the rate of reaction drops to zero at 60°C.
_________________________________________________________________________ [3]
15. Pepsin is an enzyme found in the human stomach.
(a) State the optimum pH for pepsin activity.
_________________________________________________________________________ [1]
(b) Explain what happens to pepsin if it is moved to the small intestine where the pH is approximately 8.
_________________________________________________________________________ [3]
Section D: Application and Synthesis (Questions 16–20)
16. A patient suffers from a genetic condition where their cells lack functional lysosomes.
(a) State the normal function of lysosomes.
_________________________________________________________________________ [1]
(b) Predict the effect of this condition on the cell’s ability to remove waste.
_________________________________________________________________________ [2]
17. In an investigation, students tested the effect of substrate concentration on enzyme activity. The results showed that the rate of reaction increased and then plateaued.
(a) Explain why the rate of reaction plateaued at high substrate concentrations.
_________________________________________________________________________ [3]
(b) Suggest one way to increase the rate of reaction after the plateau has been reached.
_________________________________________________________________________ [1]
18. Cyanide is a poison that inhibits mitochondrial function.
(a) Explain why cyanide poisoning leads to cell death.
_________________________________________________________________________ [3]
19. Fig. 19.1 shows a dialysis tubing experiment. The tubing contains starch and glucose solution and is placed in a beaker of distilled water. After 30 minutes, the water in the beaker is tested.
(a) State which molecule(s) will be found in the beaker water.
_________________________________________________________________________ [1]
(b) Explain your answer based on the size of the molecules and the nature of the membrane.
_________________________________________________________________________ [3]
20. Explain why enzymes are specific to their substrates. Refer to the structure of the enzyme in your answer.
_________________________________________________________________________ [3]
End of Quiz
Answers
Secondary 4 Pure Biology Quiz - Cells Biomolecules: Answer Key
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 due to osmotic pressure [1] (c) Cell Y is an animal cell (or non-photosynthetic cell) [1]. Chloroplasts are required for photosynthesis, which animal cells do not perform [1].
3. (a) Haemoglobin [1] (b) Increases surface area to volume ratio [1], allowing for faster diffusion of oxygen into and out of the cell [1]. (c) Provides more space for haemoglobin [1], allowing the cell to carry more oxygen [1].
4. (a) Osmosis [1] (b) The long projection increases the surface area [1] for absorption, allowing water to enter the cell at a faster rate [1].
5.
- Nucleus: Absent (No true nucleus) / Present (True nucleus with membrane) [1]
- Ribosomes: Smaller (70S) / Larger (80S) [1] (Note: Accept "Present" for both if distinction not made, but distinction is preferred)
- Mitochondria: Absent / Present [1]
6. Diffusion is the net movement [1] of particles from a region of higher concentration to a region of lower concentration [1], down a concentration gradient.
7. (a) Volume increases / Tubing swells [1] (b) The sugar solution inside has a lower water potential than the distilled water outside [1]. Water moves by osmosis [1] from the region of higher water potential (outside) to lower water potential (inside) through the partially permeable membrane [1].
8. (a) The movement of substances from a region of lower concentration to a region of higher concentration [1], against a concentration gradient, using energy [1]. (b) 1. Energy (ATP) [1] 2. Carrier proteins [1] (c) Mitochondria produce energy (ATP) via respiration [1]. Active transport requires energy to pump ions against the gradient [1].
9. (a) Solution P [1] (b) Solution R has a lower water potential than the potato cell sap [1]. Water moves out of the potato cells by osmosis [1]. The cells lose turgor pressure and become flaccid/plasmolysed [1].
10. (a) Active transport [1] (b) Diffusion only moves substances down a concentration gradient (high to low) [1]. Here, ions are moving from low concentration (soil) to high concentration (cell), which is against the gradient [1].
11.
- Starch Building Block: Glucose [1]
- Starch Test: Iodine Solution [1]
- Protein Building Block: Amino Acids [1]
- Fat Test: Ethanol (Emulsion test) [1]
12. Add Benedict’s solution to the food sample [1]. Heat the mixture in a water bath (boil) [1]. A positive result is indicated by a colour change from blue to green/yellow/orange/brick-red precipitate [1]. The specific colour depends on the amount of sugar [1].
13. (a) A substance that speeds up the rate of a chemical reaction [1] without being used up or changed in the process [1]. (b) The substrate has a specific shape that fits into the enzyme’s active site [1], like a key fits into a lock [1]. This forms an enzyme-substrate complex [1]. The reaction occurs, and products are released, leaving the enzyme unchanged [1].
14. (a) As temperature increases, kinetic energy of enzyme and substrate molecules increases [1]. This leads to more frequent collisions [1] and more enzyme-substrate complexes forming per unit time [1]. (b) High temperature breaks the bonds holding the enzyme structure together [1]. The enzyme denatures [1]. The shape of the active site changes [1]. The substrate can no longer fit into the active site [1]. (Any 3)
15. (a) pH 2 (Acidic) [1] (b) Pepsin will denature [1]. The high pH (alkaline) changes the shape of the active site [1]. Pepsin can no longer bind to its substrate/protein [1].
16. (a) Digestion of waste materials / Breakdown of worn-out organelles / Digestion of pathogens [1] (b) Waste materials/organelles will accumulate in the cell [1]. This may lead to cell dysfunction or death [1].
17. (a) All active sites of the enzyme molecules are occupied/saturated [1]. Adding more substrate cannot increase the rate because there are no free active sites available [1]. The rate is limited by enzyme concentration [1]. (b) Increase the enzyme concentration [1].
18. Mitochondria are the site of aerobic respiration [1]. Cyanide stops ATP production [1]. Cells require ATP for essential life processes (e.g., active transport, synthesis) [1]. Without energy, cells cannot function and die [1]. (Any 3)
19. (a) Glucose [1] (b) Glucose molecules are small enough to pass through the pores of the partially permeable membrane [1]. Starch molecules are large polysaccharides [1] and are too big to pass through the membrane pores [1].
20. Enzymes have a specific 3D shape [1]. The active site has a unique shape complementary to only one specific substrate [1]. Only the correct substrate can fit into the active site to form an enzyme-substrate complex [1].