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Secondary 4 Combined Science Biology Preliminary Examination Paper 3
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Questions
TuitionGoWhere Practice Paper - Combined Science Biology Secondary 4
TuitionGoWhere Secondary School (AI)
Subject: Combined Science (Biology)
Level: Secondary 4
Paper: Preliminary Examination (Version 3 of 5)
Duration: 1 hour 15 minutes
Total Marks: 65
Name: _________________________
Class: _________________________
Date: _________________________
Instructions to Candidates:
- Write your name, class, and date in the spaces above.
- Answer all questions.
- Write your answers in the spaces provided on the question paper.
- The number of marks is given in brackets [ ] at the end of each question or part question.
- You may use a calculator.
Section A: Structured Questions
Answer all questions in this section.
1. Fig. 1.1 shows a diagram of a typical animal cell and a plant cell.
(a) Identify the structure labelled X in the plant cell. [1]
(b) State one function of structure Y, which is found in both cell types. [1]
(c) Explain why structure Z is abundant in muscle cells but scarce in skin cells. [2]
2. A student investigated the effect of temperature on the activity of the enzyme amylase. The results are shown in Table 2.1.
| Temperature (°C) | Time taken for starch to disappear (s) |
|---|---|
| 20 | 180 |
| 30 | 90 |
| 40 | 45 |
| 50 | 120 |
| 60 | >300 (starch still present) |
(a) Describe the trend in enzyme activity as the temperature increases from 20°C to 40°C. [1]
(b) Explain why the time taken for starch to disappear increases significantly at 60°C. [3]
(c) Suggest why the student kept the pH constant throughout the experiment. [1]
3. Fig. 3.1 shows a cross-section of a leaf.
(a) Name the tissue layer labelled A and state one adaptation of its cells for photosynthesis. [2]
(b) Explain how the air spaces in layer B facilitate gas exchange. [2]
(c) State the process by which water vapour leaves the leaf through the stomata. [1]
4. Glucose is absorbed into the bloodstream from the small intestine.
(a) Name the process by which glucose moves from the lumen of the small intestine into the epithelial cells when the concentration of glucose is higher in the cells than in the lumen. [1]
(b) Explain why this process requires energy. [2]
(c) State the source of this energy within the cell. [1]
5. Fig. 5.1 shows the changes in the thickness of the uterine lining during one menstrual cycle.
(a) Identify the hormone responsible for the repair and thickening of the uterine lining between day 5 and day 14. [1]
(b) Describe the role of progesterone after day 14. [2]
(c) If fertilization does not occur, explain what happens to the uterine lining at the end of the cycle. [2]
6. A patient has a genetic condition where their red blood cells are sickle-shaped.
(a) State one disadvantage of sickle-shaped red blood cells compared to normal biconcave red blood cells. [1]
(b) Explain how this shape affects the transport of oxygen to body tissues. [2]
7. Carbon farming involves growing large masses of plants to absorb carbon dioxide from the atmosphere.
(a) Write the word equation for photosynthesis. [1]
(b) Explain how growing these plants helps to reduce the amount of carbon dioxide in the atmosphere. [2]
(c) Suggest one limitation of carbon farming if the plants are burned for fuel after harvesting. [1]
8. Fig. 8.1 shows a setup used to investigate osmosis using potato cylinders.
(a) Define osmosis. [2]
(b) Predict and explain the change in mass of a potato cylinder placed in a concentrated sugar solution. [3]
9. The mitochondrion is known as the "powerhouse" of the cell.
(a) State the main product of aerobic respiration that provides energy for cellular activities. [1]
(b) Explain why sperm cells contain a large number of mitochondria in their mid-piece. [2]
10. Table 10.1 shows the results of food tests performed on three unknown solutions A, B, and C.
| Solution | Iodine Test | Benedict's Test (heated) | Biuret Test |
|---|---|---|---|
| A | Blue-black | Blue | Purple |
| B | Brown | Brick-red precipitate | Blue |
| C | Brown | Blue | Purple |
(a) Identify the nutrient present in solution A. [1]
(b) Identify the nutrient present in solution B. [1]
(c) Solution C contains protein but no starch or reducing sugar. Describe how you would confirm the presence of protein using the Biuret test. [2]
Section B: Free Response Questions
Answer all questions in this section.
11. Describe in detail the pathway of an oxygen molecule from the air in the alveoli to a muscle cell in the leg. Include the names of the structures involved and the processes of transport. [6]
12. Enzymes are biological catalysts. (a) Explain the "lock and key" hypothesis of enzyme action. [3]
(b) Discuss how pH affects enzyme activity, referring to the active site. [3]
13. Compare and contrast diffusion and active transport. Include references to energy requirements, concentration gradients, and the involvement of membrane proteins. [6]
14. Explain the importance of maintaining a constant blood glucose concentration in the human body. Describe the roles of insulin and glucagon in this homeostatic control. [7]
15. A student observed a leaf under a microscope and noted that the upper surface was darker green than the lower surface. (a) Explain this observation in terms of chloroplast distribution. [3]
(b) Suggest how this distribution benefits the plant. [2]
Section C: Data-Based Question
Answer all questions in this section.
16. Fig. 16.1 shows the effect of light intensity on the rate of photosynthesis of a plant at two different temperatures (20°C and 30°C).
(a) Describe the effect of increasing light intensity on the rate of photosynthesis at 20°C up to point X. [2]
(b) Explain why the rate of photosynthesis levels off after point X at 20°C. [2]
(c) Suggest why the rate of photosynthesis is higher at 30°C than at 20°C between points X and Y. [2]
(d) Predict what would happen to the rate of photosynthesis if the temperature was increased to 50°C. Explain your answer. [3]
17. Table 17.1 shows the concentration of glucose in the blood of a person before and after eating a meal containing carbohydrates.
| Time (minutes) | Blood Glucose Concentration (mg/100cm³) |
|---|---|
| 0 | 90 |
| 30 | 140 |
| 60 | 110 |
| 90 | 90 |
| 120 | 90 |
(a) Explain the increase in blood glucose concentration between 0 and 30 minutes. [2]
(b) Explain the decrease in blood glucose concentration between 30 and 90 minutes. [3]
(c) Name the organ responsible for monitoring blood glucose levels. [1]
18. Fig. 18.1 shows a pedigree chart for a genetic disease caused by a recessive allele.
(a) Define the term 'recessive allele'. [1]
(b) Using the letters N (dominant) and n (recessive), deduce the genotype of individual 5. [1]
(c) Explain your answer to (b). [2]
(d) Calculate the probability that individuals 3 and 4 will have another child with the disease. Show your working. [2]
19. Bile is produced by the liver and stored in the gall bladder.
(a) State where bile is released into during digestion. [1]
(b) Explain the role of bile in the digestion of fats. [3]
(c) Why is bile not considered an enzyme? [1]
20. Cell division is essential for growth and repair.
(a) Name the type of cell division that produces genetically identical daughter cells. [1]
(b) State one importance of this type of cell division in multicellular organisms. [1]
(c) Describe the arrangement of chromosomes in the nucleus of a cell before division begins. [2]
End of Paper
Answers
TuitionGoWhere Practice Paper - Combined Science Biology Secondary 4
Answer Key & Marking Scheme Paper: Preliminary Examination (Version 3 of 5)
Section A: Structured Questions
1. (a) Cell wall / Chloroplast / Vacuole (Accept any one correct plant-specific structure if labelled correctly in standard diagrams, but typically X refers to Cell Wall or Chloroplast in this context. Assuming standard diagram: Chloroplast or Cell Wall). Note: Without the visual, standard answer is usually Cell Wall or Chloroplast. Let's assume X is Chloroplast for specificity. -> Chloroplast [1] (b) Nucleus (if Y is nucleus): Controls cell activities / Contains genetic material. OR Cell Membrane: Controls entry/exit of substances. [1] (c) Muscle cells require more energy (ATP) for contraction [1]; Mitochondria are the site of aerobic respiration/ATP production [1].
2. (a) The time taken decreases / Rate of reaction increases [1]. (b) At 60°C, the enzyme is denatured [1]; The shape of the active site changes [1]; Substrate (starch) can no longer fit/bind to the active site [1]. (c) pH is a variable that affects enzyme activity / To ensure it is a fair test / To keep pH as a controlled variable [1].
3. (a) Palisade mesophyll [1]; Contains many chloroplasts / Tightly packed / Columnar shape to maximize light absorption [1]. (b) Air spaces allow for rapid diffusion of gases (CO₂ and O₂) [1]; They connect to stomata for gas exchange with the atmosphere [1]. (c) Transpiration [1].
4. (a) Active transport [1]. (b) Glucose is moved against the concentration gradient (from low to high concentration) [1]; This requires energy to pump molecules [1]. (c) Respiration (producing ATP) [1].
5. (a) Oestrogen [1]. (b) Maintains the thickness of the uterine lining [1]; Prepares the uterus for implantation of the embryo [1]. (c) Progesterone levels drop [1]; The uterine lining breaks down/sheds (menstruation) [1].
6. (a) Reduced surface area for gas exchange / Cells block capillaries / Shorter lifespan [1]. (b) Less hemoglobin can be carried / Blood flow is restricted/blocked in capillaries [1]; Less oxygen is delivered to tissues [1].
7. (a) Carbon dioxide + Water → Glucose + Oxygen (in the presence of light and chlorophyll) [1]. (b) Plants use carbon dioxide as a raw material for photosynthesis [1]; Carbon is stored in the plant biomass (stems/leaves/roots) [1]. (c) Burning releases the stored carbon dioxide back into the atmosphere [1].
8. (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) through a partially permeable membrane [1]. (b) The potato cylinder will lose mass [1]; Water moves out of the potato cells by osmosis [1] because the sugar solution has a lower water potential than the cell sap [1].
9. (a) ATP (Adenosine Triphosphate) [1]. (b) Sperm cells need energy for movement/swimming [1]; Mitochondria provide the ATP required for the tail to move [1].
10. (a) Starch and Protein [1] (Must identify both if implied by "nutrient present" generally, but usually asks for specific. A has Starch (Iodine +) and Protein (Biuret +). Question asks for "the nutrient". If singular, accept Starch or Protein. Better: Starch and Protein). Correction: Question asks for "the nutrient" singular. Usually, these questions target the positive result. Let's assume it asks for the main carbohydrate or just identification. Accept Starch or Protein. Given A is Blue-black (Starch) and Purple (Protein), listing both is safest. If forced to one, context usually implies the carbohydrate test first. Let's accept Starch or Protein. [1] (b) Reducing Sugar (e.g., Glucose) [1]. (c) Add Biuret reagent (Sodium hydroxide and Copper(II) sulfate) [1]; Solution turns purple/lilac if protein is present [1].
Section B: Free Response Questions
11.
- Oxygen diffuses from alveoli into blood capillaries [1].
- Binds to hemoglobin in red blood cells [1].
- Transported via pulmonary vein to left atrium [1].
- Left atrium to left ventricle [1].
- Left ventricle pumps blood into aorta [1].
- Aorta branches into arteries leading to the leg [1].
- Diffuses from capillaries in muscle tissue into muscle cells [1]. (Max 6 marks. Must mention diffusion, hemoglobin, heart chambers, aorta, and final diffusion into cell.)
12. (a)
- Enzyme has a specific active site shape [1].
- Substrate has a complementary shape [1].
- Substrate fits into active site like a key in a lock to form an enzyme-substrate complex [1].
(b)
- Changes in pH affect the charges on the amino acids in the enzyme [1].
- This alters the shape of the active site [1].
- If the shape changes significantly (denaturation), the substrate no longer fits [1].
13.
- Diffusion: Passive process (no energy) [1]; Moves down concentration gradient (high to low) [1]; Does not require carrier proteins (simple diffusion) or uses channel proteins (facilitated) [1].
- Active Transport: Requires energy (ATP) [1]; Moves against concentration gradient (low to high) [1]; Requires specific carrier proteins [1]. (1 mark for each correct contrasting point. Max 6.)
14.
- Important to ensure cells have a constant supply of glucose for respiration [1] and to prevent damage to cells/organs (e.g., kidneys, eyes) from high glucose [1].
- High Glucose: Pancreas (beta cells) detects high glucose [1]; Secretes insulin [1]; Insulin causes liver/muscle cells to take up glucose and convert it to glycogen [1]; Blood glucose decreases.
- Low Glucose: Pancreas (alpha cells) detects low glucose [1]; Secretes glucagon [1]; Glucagon causes liver to convert glycogen to glucose [1]; Blood glucose increases. (Max 7 marks. Need clear negative feedback loop explanation.)
15. (a)
- Palisade mesophyll cells are located in the upper part of the leaf [1].
- They contain more chloroplasts than the spongy mesophyll cells in the lower part [1].
- Chlorophyll in chloroplasts is green [1].
(b)
- Upper surface receives more direct sunlight [1].
- More chloroplasts maximize light absorption for photosynthesis [1].
Section C: Data-Based Question
16. (a) The rate of photosynthesis increases linearly/proportionally with light intensity [1]; Light is the limiting factor [1]. (b) Another factor becomes limiting (e.g., CO₂ concentration or temperature) [1]; Increasing light further cannot increase the rate because the enzymes are working at maximum capacity [1]. (c) Higher temperature increases the kinetic energy of enzyme and substrate molecules [1]; More frequent successful collisions occur [1]; (Up to the optimum temperature). (d) The rate would decrease significantly/drop to zero [1]; Enzymes would be denatured [1]; Active site shape changes, preventing substrate binding [1].
17. (a) Carbohydrates in the meal are digested into glucose [1]; Glucose is absorbed into the bloodstream from the small intestine [1]. (b) Pancreas detects high blood glucose [1]; Secretes insulin [1]; Insulin promotes uptake of glucose by cells and conversion to glycogen in the liver [1]. (c) Pancreas [1].
18. (a) An allele that is only expressed in the phenotype when two copies are present (homozygous) / Masked by a dominant allele [1]. (b) Nn (Heterozygous) [1]. (c) Individual 5 is unaffected (shows dominant phenotype) [1] but has an affected parent/child (must inherit recessive allele) OR Individual 5 has an affected child (nn), so 5 must contribute an 'n' allele [1]. Note: Depending on pedigree structure. Standard logic: If 5 is unaffected but has affected offspring or parents, 5 is Nn. (d) If 3 and 4 are both Nn (carriers):
- Genetic cross: Nn x Nn [1].
- Offspring probabilities: NN, Nn, Nn, nn.
- Probability of disease (nn) is 1/4 or 25% [1].
19. (a) Duodenum / Small intestine [1]. (b) Bile salts emulsify fats [1]; Breaks large fat droplets into smaller droplets [1]; Increases surface area for lipase action [1]. (c) It does not break down fats chemically / It does not change the chemical structure of fats / It is not a protein catalyst [1].
20. (a) Mitosis [1]. (b) Growth / Repair of tissues / Asexual reproduction [1]. (c) Chromosomes are visible as distinct threads [1]; They are duplicated (consist of two chromatids) [1].