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Secondary 3 Combined Science Life Sciences Quiz

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Questions

Secondary 3 Combined Science Quiz - Life Sciences

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 is shown in brackets [ ] at the end of the question or part-question.
Use scientific terminology where appropriate.

Section A: Multiple Choice & Short Answer (Questions 1-5)

1. Which of the following correctly describes the movement of substances during osmosis?
A. Water molecules move from a region of lower water potential to a region of higher water potential through a partially permeable membrane.
B. Water molecules move from a region of higher water potential to a region of lower water potential through a partially permeable membrane.
C. Solute molecules move from a region of higher concentration to a region of lower concentration through a partially permeable membrane.
D. Solute molecules move from a region of lower concentration to a region of higher concentration through a partially permeable membrane.

[1]

2. A student observes a plant cell under a microscope after placing it in a concentrated salt solution for 30 minutes. The cytoplasm has shrunk away from the cell wall. What is the state of this cell?
A. Turgid
B. Flaccid
C. Plasmolysed
D. Haemolysed

[1]

3. Which enzyme is responsible for breaking down proteins into amino acids in the human digestive system?
A. Amylase
B. Lipase
C. Protease
D. Maltase

[1]

4. In the human heart, which vessel carries oxygenated blood from the lungs to the heart?
A. Aorta
B. Pulmonary Artery
C. Pulmonary Vein
D. Vena Cava

[1]

5. State the primary function of the xylem tissue in plants.

[1]

Section B: Structured Questions - Physiology & Transport (Questions 6-10)

6. Name the process by which plants lose water vapour through the stomata.

[1]

7. During aerobic respiration in humans, glucose is broken down in the presence of oxygen. Write the word equation for aerobic respiration.

[2]

8. Identify the main force responsible for pulling water up the xylem vessels in a tall tree.

[1]

9. Which part of the human digestive system is the primary site for the absorption of nutrients?

[1]

10. State one structural adaptation of the red blood cell that allows it to carry oxygen efficiently.

[1]

Section C: Structured Questions - Processes & Enzymes (Questions 11-15)

11. The diagram below (not shown, described) represents a setup to investigate the effect of light intensity on the rate of photosynthesis in an aquatic plant (Elodea). Bubbles of gas are collected in a test tube.

(a) Name the gas collected in the test tube.
_________________________________________________________________________ [1]

(b) The student varies the distance of the lamp from the plant.
(i) State the relationship between the distance of the lamp and the light intensity.
_________________________________________________________________________ [1]
(ii) Suggest one variable, other than light intensity, that must be kept constant in this experiment.
_________________________________________________________________________ [1]

_________________________________________________________________________ [2]

12. Table 1 shows the relative amounts of amino acids and maltose found in a person’s alimentary canal as food passes through different regions.

Region	Amount of Amino Acids	Amount of Maltose
Stomach	Low	Low
Duodenum (Start of Small Intestine)	Increasing	High
Ileum (End of Small Intestine)	Low	Low

(a) Explain why the amount of amino acids increases in the duodenum.

_________________________________________________________________________ [2]

(b) Explain why the amount of amino acids decreases in the ileum.

_________________________________________________________________________ [2]

(c) Maltose is a disaccharide. Name the enzyme that breaks down maltose and the product of this digestion.
Enzyme: __________________________
Product: __________________________ [2]

13. Figure 1 shows a cross-section of the human heart.

(a) Describe the pathway of blood from the lungs to the aorta. Include the names of the chambers and valves involved.

_________________________________________________________________________ [4]

(b) Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.

_________________________________________________________________________ [2]

14. A student investigates the effect of temperature on the activity of the enzyme amylase. The time taken for starch to be completely broken down is recorded at different temperatures.

(a) Define the term 'enzyme'.

_________________________________________________________________________ [2]

(b) At 70°C, the enzyme activity stops completely. Explain why this happens using the concept of enzyme structure.

_________________________________________________________________________ [3]

15. Compare and contrast aerobic and anaerobic respiration in humans. Your answer should include:

The word equations for both processes.
The difference in energy yield.
The conditions under which anaerobic respiration occurs in humans.

_________________________________________________________________________ [6]

Section D: Free Response & Data Analysis (Questions 16-20)

16. Root hair cells are specialised for the absorption of water and mineral ions from the soil.

(a) Describe two structural adaptations of root hair cells that facilitate this function.

_________________________________________________________________________ [2]

(b) Explain how mineral ions are absorbed into root hair cells when the concentration of ions in the soil is lower than in the cell sap.

_________________________________________________________________________ [2]

17. A student places a strip of potato tissue into a concentrated sugar solution. After one hour, the potato strip becomes flexible and shorter.

(a) Explain these changes in terms of water potential and osmosis.

_________________________________________________________________________ [3]

(b) If the potato strip were placed in distilled water instead, describe and explain what would happen to the cells.

_________________________________________________________________________ [2]

18. The human circulatory system is described as a double circulatory system.

(a) Define what is meant by a "double circulatory system".

_________________________________________________________________________ [2]

(b) State one advantage of having a double circulatory system compared to a single circulatory system (like in fish).

_________________________________________________________________________ [1]

19. Enzymes are sensitive to pH changes. Pepsin is an enzyme found in the stomach.

(a) State the optimum pH condition for pepsin activity.
_________________________________________________________________________ [1]

(b) Explain what would happen to the rate of reaction of pepsin if it were moved to the small intestine (pH 8).

_________________________________________________________________________ [2]

20. Transpiration rate is affected by environmental conditions.

(a) List two environmental factors, other than light intensity, that affect the rate of transpiration.

__________________________ [2]

(b) Explain how high humidity affects the rate of transpiration.

_________________________________________________________________________ [2]

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Answers

Secondary 3 Combined Science Quiz - Life Sciences (Answer Key)

1. B
[1] Water moves from high water potential (dilute) to low water potential (concentrated) via a partially permeable membrane.

2. C
[1] Plasmolysis occurs when water leaves the cell, causing the cytoplasm to shrink away from the cell wall.

3. C
[1] Protease breaks down proteins. Amylase breaks down starch; Lipase breaks down fats.

4. C
[1] Pulmonary veins carry oxygenated blood from lungs to the left atrium. Pulmonary arteries carry deoxygenated blood to lungs.

5. Transport of water and mineral salts (from roots to leaves) / Provide mechanical support.
[1] Accept either function.

6. Transpiration
[1]

7. Glucose + Oxygen → Carbon Dioxide + Water (+ Energy)
[2] 1 mark for correct reactants, 1 mark for correct products. Energy is optional but good practice.

8. Transpiration pull
[1]

9. Small Intestine (or Ileum)
[1]

10. Biconcave shape (increases surface area for diffusion) / No nucleus (more space for haemoglobin) / Thin membrane (short diffusion distance).
[1] Any one valid adaptation.

11.
(a) Oxygen
[1]
(b) (i) As distance increases, light intensity decreases (inverse square law).
[1]
(ii) Temperature / Carbon dioxide concentration / Type of plant / Volume of water.
[1]
(c) To prevent heat from the lamp from raising the temperature of the water/plant.
[1] This ensures temperature remains a controlled variable / constant.
[1]

12.
(a) Proteins are digested by protease (in stomach/duodenum) into amino acids.
[1] Therefore, the concentration of amino acids increases as digestion proceeds.
[1]
(b) Amino acids are absorbed into the blood capillaries / villi.
[1] Through the wall of the small intestine (ileum).
[1]
(c) Enzyme: Maltase
[1]
Product: Glucose
[1]

13.
(a) Blood returns from lungs via pulmonary veins to the left atrium.
[1] Left atrium contracts, pushing blood through the bicuspid/mitral valve into the left ventricle.
[1] Left ventricle contracts.
[1] Blood is forced through the aortic valve into the aorta.
[1]
(b) The left ventricle pumps blood to the whole body (systemic circulation), which requires higher pressure.
[1] The right ventricle only pumps blood to the lungs (pulmonary circulation), which is a shorter distance/lower resistance.
[1] Therefore, the left ventricle muscle needs to be thicker/stronger.

14.
(a) Enzymes are biological catalysts.
[1] They are proteins that speed up chemical reactions without being used up.
[1]
(b) At 70°C, the high temperature breaks the bonds holding the enzyme's structure together.
[1] The active site changes shape (denaturation).
[1] The substrate can no longer fit into the active site (lock and key hypothesis fails), so no reaction occurs.
[1]

15.
Equations:
Aerobic: Glucose + Oxygen → Carbon Dioxide + Water
[1]
Anaerobic (Human): Glucose → Lactic Acid
[1]
Energy Yield:
Aerobic respiration releases a large amount of energy (ATP).
[1]
Anaerobic respiration releases a small amount of energy (ATP).
[1]
Conditions:
Anaerobic respiration occurs in muscle cells during vigorous exercise when oxygen supply is insufficient.
[1]
Oxygen debt is incurred and must be repaid later.
[1]
(Max 6 marks. Award marks for clear comparison.)

16.
(a) 1. Long hair-like projection increases surface area for absorption.
[1]
2. Thin cell wall / membrane allows for short diffusion distance / fast uptake.
[1]
(Alternative: Large vacuole maintains concentration gradient.)
(b) Active transport.
[1]
Mineral ions are moved against the concentration gradient (from low to high concentration).
[1]
This process requires energy (ATP) from respiration.
[1]
(Note: Question asks for explanation of absorption when soil conc is lower, implying active transport.)

17.
(a) The sugar solution has a lower water potential than the potato cells.
[1] Water moves out of the potato cells by osmosis.
[1] The cells lose turgor pressure / become plasmolysed, causing the strip to become flexible and shorter.
[1]
(b) The cells would become turgid / firm.
[1] Water enters the cells by osmosis because distilled water has a higher water potential than the cell sap. The cell wall prevents bursting.
[1]

18.
(a) Blood passes through the heart twice for every complete circuit of the body.
[1] (Once to the lungs and once to the rest of the body).
[1]
(b) It allows blood to be pumped at higher pressure to the body tissues.
[1] (Or: Oxygenated and deoxygenated blood do not mix, ensuring efficient oxygen delivery).

19.
(a) Acidic / Low pH (around pH 2).
[1]
(b) The rate of reaction would decrease significantly or stop.
[1] Pepsin is denatured at alkaline pH / the active site changes shape.
[1]

20.
(a) Temperature, Wind speed / Air movement, Humidity.
[1] Any two.
[1]
(b) High humidity means the air outside the leaf has a high water potential / is saturated with water vapour.
[1] This reduces the concentration gradient between the inside and outside of the leaf, slowing down the diffusion of water vapour out of the stomata.
[1]