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Secondary 4 Combined Science Biology Preliminary Examination Paper 1
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Questions
TuitionGoWhere Secondary School (AI)
Preliminary Examination 2024
Subject: Combined Science Biology
Level: Secondary 4
Paper: Paper 3 (Biology)
Duration: 1 hour 15 minutes
Total Marks: 65 marks
Name: _________________ Class: _________ Date: _________
Instructions to Candidates
- Answer ALL questions in the spaces provided
- Show all working clearly for calculation questions
- Use appropriate scientific terminology
- Diagrams should be clearly labeled where required
Section A: Multiple Choice Questions [8 marks]
For each question, choose the best answer and write the letter in the box provided.
1. Which process allows carbon dioxide to move from blood into alveolar air?
A. Active transport
B. Diffusion
C. Osmosis
D. Filtration
Answer: [ ]
2. The table shows organelle counts in different cell types:
| Cell Type | Mitochondria | Ribosomes |
|---|---|---|
| Muscle cell | 1200 | 800 |
| Pancreatic cell | 300 | 2000 |
| Red blood cell | 0 | 0 |
Which statement best explains these differences? A. All cells have the same energy requirements B. Cell function determines organelle number C. Larger cells always have more organelles D. Organelle number is random
Answer: [ ]
3. During photosynthesis, which process occurs in the chloroplasts?
A. Only light-dependent reactions
B. Only light-independent reactions
C. Both light-dependent and light-independent reactions
D. Neither light-dependent nor light-independent reactions
Answer: [ ]
4. Which hormone maintains the uterine lining during pregnancy? A. Oestrogen only B. Progesterone only C. Both oestrogen and progesterone D. Neither oestrogen nor progesterone
Answer: [ ]
Section B: Structured Response Questions [32 marks]
5. The diagram shows a cross-section through a leaf.
a) (i) Name the layer labeled X. [1]
(ii) Explain why layer X contains more chloroplasts than layer Y. [3]
b) Describe how the structure of layer Y is adapted for gas exchange. [2]
6. A student investigated the effect of carbon dioxide concentration on the rate of photosynthesis in aquatic plants. The results are shown in the graph below.
a) Describe the relationship between CO₂ concentration and photosynthesis rate shown in the graph. [2]
b) Explain why the rate of photosynthesis levels off at high CO₂ concentrations. [2]
c) Suggest TWO other factors that could limit the rate of photosynthesis. [2]
(i) _________________________________________________
(ii) _________________________________________________
7. The table shows the number of mitochondria in different human cell types:
| Cell Type | Average number of mitochondria |
|---|---|
| Liver cell | 1000 |
| Muscle cell | 1500 |
| Skin cell | 200 |
| Sperm cell | 100 |
a) Suggest why muscle cells have more mitochondria than skin cells. [2]
b) Explain why sperm cells have relatively few mitochondria despite being motile. [2]
8. Describe the process by which glucose moves from the small intestine into the blood against its concentration gradient. Include the following in your answer:
- Name of the process
- Energy requirement
- Type of proteins involved [4]
9. The graph shows changes in blood glucose concentration and hormone levels during a glucose tolerance test.
a) Name hormones A and B. [2]
Hormone A: _________________________________________________
Hormone B: _________________________________________________
b) Explain how hormone A helps to reduce blood glucose concentration. [3]
c) Describe what would happen to blood glucose levels if hormone A was not produced. [2]
10. Explain the role of bile salts in lipid digestion. Include in your answer:
- The process of emulsification
- How this aids enzyme action
- The final products of lipid digestion [4]
Section C: Extended Response Questions [25 marks]
11. Describe in detail the pathway taken by an oxygen molecule from the air in the lungs to a muscle cell where it is used in respiration. Name all the structures involved and explain the processes that occur at each stage. [8]
12. The menstrual cycle is controlled by hormones that regulate changes in the ovaries and uterus.
a) Describe the changes that occur in the uterine lining during one complete menstrual cycle (28 days). [4]
b) Explain the roles of oestrogen and progesterone in controlling these changes. Include in your answer how these hormones interact with each other. [6]
13. Scientists are investigating "carbon farming" using fast-growing plants that absorb large amounts of carbon dioxide.
Using your knowledge of photosynthesis and ecosystems, evaluate the potential benefits and limitations of this approach to reducing atmospheric CO₂ levels. [7]
END OF PAPER
Answers
TuitionGoWhere Secondary School (AI)
Preliminary Examination 2024 - MARKING SCHEME
Subject: Combined Science Biology
Level: Secondary 4
Paper: Paper 3 (Biology)
Total Marks: 65 marks
Section A: Multiple Choice Questions [8 marks]
1. B. Diffusion [2 marks] Marking: 2 marks for correct answer
2. B. Cell function determines organelle number [2 marks]
Marking: 2 marks for correct answer
3. C. Both light-dependent and light-independent reactions [2 marks] Marking: 2 marks for correct answer
4. C. Both oestrogen and progesterone [2 marks] Marking: 2 marks for correct answer
Section B: Structured Response Questions [32 marks]
5a(i) Name layer X [1] Answer: Palisade mesophyll/palisade layer Marking: 1 mark for correct identification
5a(ii) Why layer X has more chloroplasts than layer Y [3] Answer: Layer X (palisade) is positioned at the top of the leaf where it receives direct sunlight/maximum light intensity. More chloroplasts are needed to capture light energy for photosynthesis. Layer Y (spongy mesophyll) receives less direct light so fewer chloroplasts are sufficient. Marking: 1 mark for light exposure; 1 mark for photosynthesis function; 1 mark for comparison
5b Structure of layer Y adapted for gas exchange [2] Answer: Layer Y has large air spaces/intercellular spaces that allow gases to move freely. The loosely packed cells provide a large surface area for gas exchange. Marking: 1 mark for air spaces; 1 mark for surface area/gas movement
6a Relationship between CO₂ and photosynthesis rate [2] Answer: As CO₂ concentration increases, the rate of photosynthesis increases initially, then levels off/plateaus at higher concentrations. Marking: 1 mark for initial increase; 1 mark for leveling off
6b Why rate levels off at high CO₂ [2] Answer: Another factor becomes limiting, such as light intensity or temperature. CO₂ is no longer the limiting factor. Marking: 1 mark for limiting factor concept; 1 mark for naming another factor
6c Two other limiting factors [2] Answer: (i) Light intensity (ii) Temperature Marking: 1 mark each for any two: light intensity, temperature, chlorophyll concentration
7a Why muscle cells have more mitochondria [2] Answer: Muscle cells require more ATP/energy for muscle contraction. More mitochondria are needed to carry out cellular respiration to produce this ATP. Marking: 1 mark for energy/ATP requirement; 1 mark for linking to cell function
7b Why sperm cells have few mitochondria [2] Answer: Sperm cells are small and have limited space. They have a short lifespan and only need energy for a brief period of motility. Marking: 1 mark for size constraint; 1 mark for short lifespan/brief energy need
8 Glucose transport process [4] Answer: The process is active transport. It requires energy in the form of ATP because glucose moves against its concentration gradient (from low to high concentration). Carrier proteins/transport proteins in the cell membrane are involved in moving glucose molecules. Marking: 1 mark for active transport; 1 mark for ATP/energy; 1 mark for against gradient; 1 mark for carrier proteins
9a Name hormones A and B [2] Answer: Hormone A: Insulin; Hormone B: Glucagon Marking: 1 mark each for correct identification
9b How hormone A reduces blood glucose [3] Answer: Insulin increases glucose uptake by muscle and adipose tissue cells. It promotes the conversion of glucose to glycogen in the liver (glycogenesis). It also promotes glucose use in cellular respiration. Marking: 1 mark for increased uptake; 1 mark for glycogen synthesis; 1 mark for glucose utilization
9c What happens without hormone A [2] Answer: Blood glucose levels would remain high/increase further. Glucose would not be taken up efficiently by cells, leading to hyperglycemia. Marking: 1 mark for high glucose levels; 1 mark for poor cellular uptake
10 Role of bile salts in lipid digestion [4] Answer: Bile salts emulsify large fat droplets into smaller droplets, increasing the surface area. This allows lipase enzymes to work more efficiently on the fats. The final products are fatty acids and glycerol, which can be absorbed. Marking: 1 mark for emulsification; 1 mark for increased surface area; 1 mark for enzyme efficiency; 1 mark for products
Section C: Extended Response Questions [25 marks]
11 Oxygen pathway to muscle cell [8] Answer:
- Oxygen enters alveoli during inhalation
- Diffuses across alveolar epithelium into pulmonary capillaries
- Binds to haemoglobin in red blood cells
- Transported via pulmonary vein to left atrium, then left ventricle
- Pumped through aorta to muscle arteries and arterioles
- Diffuses from capillaries into tissue fluid
- Diffuses across muscle cell membrane
- Enters mitochondria where it is used in aerobic respiration
Marking: 1 mark each for: alveolar entry, alveolar diffusion, haemoglobin binding, heart circulation, arterial transport, capillary diffusion, cell membrane crossing, mitochondrial use
12a Changes in uterine lining during cycle [4] Answer: Days 1-5: Menstruation occurs, lining breaks down and is shed. Days 6-14: Lining rebuilds and thickens due to cell proliferation. Days 15-28: Lining is maintained at maximum thickness, prepared for implantation. If no pregnancy occurs, cycle repeats. Marking: 1 mark each for menstruation, proliferation phase, maintenance phase, cycle completion
12b Roles of oestrogen and progesterone [6] Answer: Oestrogen is produced by developing follicles and causes the uterine lining to proliferate and thicken during the first half of the cycle. Progesterone is produced by the corpus luteum after ovulation and maintains the thickened lining during the second half. High progesterone inhibits oestrogen production through negative feedback. If pregnancy doesn't occur, progesterone levels drop, causing menstruation. The hormones work antagonistically - oestrogen builds up the lining, progesterone maintains it. Marking: 1 mark for oestrogen source and function; 1 mark for progesterone source and function; 1 mark for timing; 1 mark for negative feedback; 1 mark for what happens without pregnancy; 1 mark for interaction
13 Carbon farming evaluation [7] Answer: Benefits: Plants absorb CO₂ during photosynthesis, reducing atmospheric levels. Carbon is stored in plant biomass for extended periods. Fast-growing plants can absorb large amounts quickly. Can be combined with sustainable agriculture.
Limitations: If plants are harvested and burned for fuel, CO₂ is released back to atmosphere. Decomposition of dead plant matter also releases CO₂. Large-scale farming may compete with food production for land. May reduce biodiversity if monocultures are used. Effectiveness depends on long-term carbon storage, not just absorption.
Marking: 2 marks for benefits (CO₂ absorption, carbon storage); 2 marks for limitations (CO₂ release, land use); 2 marks for detailed explanation of processes; 1 mark for balanced evaluation
Total: 65 marks
Grade Boundaries (Suggested)
- A1: 58-65 marks (89-100%)
- A2: 52-57 marks (80-88%)
- B3: 46-51 marks (71-79%)
- B4: 39-45 marks (60-70%)
- C5: 33-38 marks (51-59%)
- C6: 26-32 marks (40-50%)