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Secondary 4 Pure Biology Practice Paper 1
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TuitionGoWhere Practice Paper - Pure Biology Secondary 4
TuitionGoWhere Practice Paper (AI)
Subject: Pure Biology
Level: Secondary 4
Paper: Practice Paper Version 1
Duration: 1 hour 45 minutes
Total Marks: 80
Name: _________________________
Class: _________________________
Date: _________________________
Instructions to Candidates
- This paper consists of three sections: Section A, Section B, and Section C.
- Answer all questions.
- Write your answers in the spaces provided.
- The number of marks is given in brackets [ ] at the end of each question or part question.
- You are advised to spend about 35 minutes on Section A, 40 minutes on Section B, and 30 minutes on Section C.
- You may use a calculator.
Section A: Multiple Choice Questions [20 marks]
Answer all questions in this section. For each question, choose the correct answer and write the letter (A, B, C, or D) in the box provided.
1. Which of the following organelles is responsible for the synthesis of proteins within a cell?
A. Mitochondrion
B. Ribosome
C. Golgi body
D. Chloroplast
[1 mark]
Answer: [ ]
2. A student placed a drop of blood into a beaker of distilled water. After a few minutes, the red blood cells burst. Which process best explains this observation?
A. Diffusion of water into the cells
B. Active transport of water out of the cells
C. Osmosis of water into the cells
D. Osmosis of water out of the cells
[1 mark]
Answer: [ ]
3. The diagram below shows the structure of a DNA nucleotide.
Which labelled part represents the nitrogenous base?
A. P
B. Q
C. R
D. S
[1 mark]
Answer: [ ]
4. Which of the following correctly pairs a food test with its positive result?
| Test | Positive Result |
|---|---|
| A. Benedict's test | Blue-black colour |
| B. Iodine test | Brick-red precipitate |
| C. Biuret test | Purple colour |
| D. Ethanol emulsion test | Orange precipitate |
[1 mark]
Answer: [ ]
5. The enzyme catalase breaks down hydrogen peroxide into water and oxygen. A student investigated the effect of pH on catalase activity. The results are shown below.
| pH | Volume of oxygen produced (cm³) |
|---|---|
| 3 | 2 |
| 5 | 8 |
| 7 | 15 |
| 9 | 10 |
| 11 | 1 |
What is the optimum pH for catalase activity?
A. pH 3
B. pH 5
C. pH 7
D. pH 9
[1 mark]
Answer: [ ]
6. Which of the following statements about active transport is correct?
A. It moves substances down a concentration gradient.
B. It does not require energy from respiration.
C. It can move substances against a concentration gradient.
D. It only occurs in plant cells.
[1 mark]
Answer: [ ]
7. A student viewed a plant cell under a light microscope and observed a large, fluid-filled space occupying most of the cell. Which structure was observed?
A. Nucleus
B. Cytoplasm
C. Vacuole
D. Chloroplast
[1 mark]
Answer: [ ]
8. Which of the following elements is found in proteins but not in carbohydrates?
A. Carbon
B. Hydrogen
C. Oxygen
D. Nitrogen
[1 mark]
Answer: [ ]
9. The lock-and-key model is used to explain enzyme action. In this model, what does the "key" represent?
A. The enzyme
B. The active site
C. The substrate
D. The product
[1 mark]
Answer: [ ]
10. A student carried out an investigation using Visking tubing filled with starch solution, placed in a beaker of distilled water containing iodine solution. After 30 minutes, the water outside the tubing remained yellow-brown, but the contents of the tubing turned blue-black. What can be concluded?
A. Starch molecules diffused out of the tubing.
B. Iodine molecules diffused into the tubing.
C. Both starch and iodine diffused across the membrane.
D. Neither starch nor iodine diffused across the membrane.
[1 mark]
Answer: [ ]
11. Which of the following structures is present in a typical plant cell but absent in a typical animal cell?
A. Cell membrane
B. Mitochondrion
C. Nucleus
D. Cell wall
[1 mark]
Answer: [ ]
12. The diagram shows an enzyme-catalysed reaction.
Substrate + Enzyme → Enzyme-Substrate Complex → Enzyme + Products
Which step requires the active site to have a specific complementary shape?
A. Formation of the enzyme-substrate complex only
B. Release of products only
C. Both formation of the enzyme-substrate complex and release of products
D. Neither formation nor release
[1 mark]
Answer: [ ]
13. A red blood cell is placed in a concentrated salt solution. Which of the following describes what happens to the cell?
A. It swells and bursts.
B. It shrinks and becomes crenated.
C. It remains unchanged.
D. It undergoes plasmolysis.
[1 mark]
Answer: [ ]
14. Which of the following correctly describes the structure of a fat molecule?
A. Three fatty acids and one glycerol molecule
B. One fatty acid and three glycerol molecules
C. Many glucose molecules joined together
D. Many amino acids joined together
[1 mark]
Answer: [ ]
15. The Benedict's test is used to detect the presence of reducing sugars. Which of the following conditions is necessary for a positive result?
A. The solution must be cooled on ice.
B. The solution must be heated in a water bath.
C. Sodium hydroxide must be added.
D. Ethanol must be added.
[1 mark]
Answer: [ ]
16. Which of the following is a function of the Golgi body?
A. Protein synthesis
B. Lipid synthesis
C. Modifying and packaging proteins for secretion
D. Producing ATP through aerobic respiration
[1 mark]
Answer: [ ]
17. A student investigated the effect of temperature on the rate of diffusion of potassium permanganate crystals in water. Which of the following would increase the rate of diffusion?
A. Using larger crystals
B. Decreasing the temperature of the water
C. Increasing the temperature of the water
D. Stirring the water less frequently
[1 mark]
Answer: [ ]
18. Which of the following statements about enzymes is correct?
A. Enzymes are used up during the reaction.
B. Enzymes can catalyse many different types of reactions.
C. Enzymes lower the activation energy of a reaction.
D. Enzymes function best at very high temperatures.
[1 mark]
Answer: [ ]
19. The diagram shows the molecular structure of a carbohydrate molecule.
[Diagram showing a chain of hexose sugar units]
This molecule is most likely to be:
A. Glucose
B. Sucrose
C. Starch
D. Glycogen
[1 mark]
Answer: [ ]
20. Which of the following best explains why muscle cells contain many mitochondria?
A. Muscle cells need to store large amounts of glycogen.
B. Muscle cells require large amounts of energy for contraction.
C. Muscle cells need to synthesise large amounts of protein.
D. Muscle cells need to transport oxygen efficiently.
[1 mark]
Answer: [ ]
Section B: Structured Questions [40 marks]
Answer all questions in this section. Write your answers in the spaces provided.
21. Fig. 1.1 shows an electron micrograph of an animal cell.
[Diagram showing organelles labelled P, Q, R, and S]
(a) Identify the organelles labelled P, Q, R, and S. [4 marks]
P: ____________________________________________
Q: ____________________________________________
R: ____________________________________________
S: ____________________________________________
(b) State the function of organelle Q. [1 mark]
(c) Explain why organelle R is described as the "powerhouse" of the cell. [2 marks]
(d) A certain type of cell produces and secretes large amounts of digestive enzymes. Explain why this cell would contain many of organelle P and many of organelle S. [3 marks]
[Total: 10 marks]
22. A student investigated the effect of sucrose concentration on the mass of potato strips. Five potato strips of equal mass were placed in sucrose solutions of different concentrations for 30 minutes. The results are shown in Table 2.1.
Table 2.1
| Concentration of sucrose solution (mol/dm³) | Initial mass (g) | Final mass (g) | Change in mass (g) | Percentage change in mass (%) |
|---|---|---|---|---|
| 0.0 | 2.50 | 2.75 | +0.25 | +10.0 |
| 0.2 | 2.50 | 2.60 | +0.10 | +4.0 |
| 0.4 | 2.50 | 2.50 | 0.00 | 0.0 |
| 0.6 | 2.50 | 2.35 | -0.15 | -6.0 |
| 0.8 | 2.50 | 2.20 | -0.30 | -12.0 |
(a) Calculate the percentage change in mass for the potato strip placed in 0.6 mol/dm³ sucrose solution. Show your working. [2 marks]
(b) Explain why the potato strip placed in 0.0 mol/dm³ sucrose solution increased in mass. [3 marks]
(c) Explain why the potato strip placed in 0.8 mol/dm³ sucrose solution decreased in mass. [3 marks]
(d) Using the results in Table 2.1, estimate the concentration of sucrose solution that is isotonic to the potato cell sap. Explain your answer. [2 marks]
[Total: 10 marks]
23. Fig. 3.1 shows the effect of temperature on the activity of enzyme X.
[Graph showing enzyme activity increasing from 0°C to 40°C, peaking at 40°C, then decreasing sharply to zero at 60°C]
(a) Describe the trend shown in the graph between 0°C and 40°C. [2 marks]
(b) Explain the trend described in part (a) with reference to kinetic energy and enzyme-substrate complex formation. [3 marks]
(c) Explain why enzyme activity decreases above 40°C. [3 marks]
(d) State the optimum temperature for enzyme X. [1 mark]
(e) Suggest why human enzymes have an optimum temperature of approximately 37°C, while enzymes from bacteria living in hot springs may have an optimum temperature of 70°C or higher. [1 mark]
[Total: 10 marks]
24. A student carried out food tests on four unknown solutions (A, B, C, and D). The results are shown in Table 4.1.
Table 4.1
| Solution | Benedict's test (after heating) | Iodine test | Biuret test | Ethanol emulsion test |
|---|---|---|---|---|
| A | Blue solution | Brown | Blue | Clear |
| B | Brick-red precipitate | Brown | Blue | Clear |
| C | Blue solution | Blue-black | Blue | Clear |
| D | Blue solution | Brown | Purple | Clear |
(a) Identify the food substance(s) present in solution B. [1 mark]
(b) Identify the food substance(s) present in solution C. [1 mark]
(c) Identify the food substance(s) present in solution D. [1 mark]
(d) Solution A gave negative results for all four tests. State what this indicates about the contents of solution A. [1 mark]
(e) A student suggested that solution B might contain both reducing sugar and starch. Explain why this conclusion is incorrect based on the results in Table 4.1. [2 marks]
(f) Describe how you would carry out the ethanol emulsion test to determine if a food sample contains fats. [4 marks]
[Total: 10 marks]
Section C: Free-Response Questions [20 marks]
Answer all questions in this section. Write your answers in the spaces provided. You are advised to spend about 30 minutes on this section.
25. Enzymes are biological catalysts that play essential roles in living organisms.
(a) Describe the structure of an enzyme and explain how its structure is related to its function. Use the lock-and-key model in your answer. [5 marks]
(b) A student investigated the effect of pH on the activity of amylase. Describe how the student could carry out this investigation. Include the variables that should be controlled and how the results could be used to determine the optimum pH. [5 marks]
[Total: 10 marks]
26. Cells need to control the movement of substances across their cell membranes to maintain a constant internal environment.
(a) Distinguish between diffusion, osmosis, and active transport. In your answer, refer to the direction of movement, energy requirements, and the types of substances transported. [6 marks]
(b) Explain the importance of active transport in the absorption of glucose by the villi in the small intestine. [4 marks]
[Total: 10 marks]
END OF PAPER
Answers
TuitionGoWhere Practice Paper - Pure Biology Secondary 4
Answer Key and Marking Scheme
Paper: Practice Paper Version 1
Total Marks: 80
Section A: Multiple Choice Questions [20 marks]
| Question | Answer | Explanation |
|---|---|---|
| 1 | B | Ribosomes are the sites of protein synthesis. Mitochondria produce ATP, Golgi body modifies and packages proteins, chloroplasts carry out photosynthesis. |
| 2 | C | Distilled water has a higher water potential than the red blood cells. Water enters the cells by osmosis, causing them to swell and burst. |
| 3 | [Based on diagram] | The nitrogenous base is the part of the nucleotide that contains nitrogen and forms complementary base pairs. |
| 4 | C | Biuret test turns purple in the presence of protein. Benedict's test gives brick-red for reducing sugars, iodine test gives blue-black for starch, ethanol emulsion test gives a cloudy white emulsion for fats. |
| 5 | C | The optimum pH is where the enzyme activity is highest. At pH 7, 15 cm³ of oxygen was produced, which is the highest volume. |
| 6 | C | Active transport moves substances against a concentration gradient using energy from respiration. |
| 7 | C | The large, fluid-filled space in a plant cell is the vacuole, which contains cell sap. |
| 8 | D | Proteins contain carbon, hydrogen, oxygen, and nitrogen (and sometimes sulfur). Carbohydrates contain only carbon, hydrogen, and oxygen. |
| 9 | C | In the lock-and-key model, the substrate is the "key" that fits into the enzyme's active site (the "lock"). |
| 10 | B | Iodine molecules are small enough to diffuse through the Visking tubing into the starch solution, causing the blue-black colour. Starch molecules are too large to diffuse out. |
| 11 | D | Plant cells have a cell wall made of cellulose; animal cells do not. Both have cell membranes, mitochondria, and nuclei. |
| 12 | A | The active site must have a specific complementary shape to the substrate for the enzyme-substrate complex to form. |
| 13 | B | In a concentrated salt solution, the water potential is lower outside the cell. Water moves out by osmosis, causing the cell to shrink and become crenated. Plasmolysis occurs in plant cells, not animal cells. |
| 14 | A | A fat molecule consists of one glycerol molecule bonded to three fatty acid molecules. |
| 15 | B | Benedict's test requires heating in a water bath for the reducing sugar to reduce the copper(II) sulfate to copper(I) oxide, producing a brick-red precipitate. |
| 16 | C | The Golgi body modifies, sorts, and packages proteins for secretion from the cell. |
| 17 | C | Increasing temperature increases the kinetic energy of particles, causing them to move faster and diffuse more quickly. |
| 18 | C | Enzymes lower the activation energy of reactions. They are not used up, are specific to one type of reaction, and denature at high temperatures. |
| 19 | C | A chain of many glucose (hexose sugar) units joined together represents a polysaccharide such as starch. Glucose is a monosaccharide, sucrose is a disaccharide. |
| 20 | B | Muscle cells require large amounts of energy (ATP) for contraction, which is produced by mitochondria through aerobic respiration. |
Marking: 1 mark per correct answer. Total = 20 marks.
Section B: Structured Questions [40 marks]
Question 21 [10 marks]
(a) Identify organelles P, Q, R, and S. [4 marks]
| Label | Organelle | Mark |
|---|---|---|
| P | Rough endoplasmic reticulum / Rough ER | 1 |
| Q | Golgi body / Golgi apparatus | 1 |
| R | Mitochondrion / Mitochondria | 1 |
| S | Ribosome(s) | 1 |
Marking notes: Accept "RER" for P. Accept "Golgi complex" for Q. Accept singular or plural forms.
(b) State the function of organelle Q. [1 mark]
Answer: The Golgi body modifies, sorts, and packages proteins (into vesicles) for secretion from the cell / for transport to other parts of the cell. [1 mark]
Marking notes: Must include reference to modifying/packaging proteins. Accept "chemically modifies and packages substances made by the ER."
(c) Explain why organelle R is described as the "powerhouse" of the cell. [2 marks]
Answer: Mitochondria are the sites of aerobic respiration [1 mark], where glucose is broken down to release energy in the form of ATP [1 mark].
Marking notes: Must mention aerobic respiration and ATP/energy release. Accept "site of cellular respiration where energy is released."
(d) Explain why a cell producing digestive enzymes would contain many of organelle P and organelle S. [3 marks]
Answer:
- Ribosomes (S) are the sites of protein synthesis [1 mark]. Digestive enzymes are proteins, so many ribosomes are needed to synthesise large amounts of these enzymes [1 mark].
- Rough endoplasmic reticulum (P) transports the proteins synthesised by ribosomes to the Golgi body for packaging and secretion [1 mark].
Marking notes: Must link ribosomes to protein synthesis and rough ER to transport. Accept reference to the cell needing to produce and secrete large quantities of protein.
Question 22 [10 marks]
(a) Calculate the percentage change in mass for 0.6 mol/dm³. [2 marks]
Answer: Percentage change = (Change in mass ÷ Initial mass) × 100 [1 mark] = (-0.15 ÷ 2.50) × 100 = -6.0% [1 mark]
Marking notes: Award 1 mark for correct formula/working, 1 mark for correct answer with negative sign. The answer is already given in the table; accept if student shows working.
(b) Explain why the potato strip in 0.0 mol/dm³ sucrose solution increased in mass. [3 marks]
Answer:
- The 0.0 mol/dm³ solution (distilled water) has a higher water potential than the potato cell sap [1 mark].
- Water enters the potato cells by osmosis, down the water potential gradient [1 mark].
- The cells become turgid, and the mass of the potato strip increases [1 mark].
Marking notes: Must mention water potential gradient and osmosis. Accept "water moves from a region of higher water potential to a region of lower water potential."
(c) Explain why the potato strip in 0.8 mol/dm³ sucrose solution decreased in mass. [3 marks]
Answer:
- The 0.8 mol/dm³ sucrose solution has a lower water potential than the potato cell sap [1 mark].
- Water moves out of the potato cells by osmosis, down the water potential gradient [1 mark].
- The cells lose turgor / become flaccid, and the mass of the potato strip decreases [1 mark].
Marking notes: Must mention water potential gradient and osmosis. Accept "water moves from a region of higher water potential (inside cells) to a region of lower water potential (outside)."
(d) Estimate the isotonic concentration and explain. [2 marks]
Answer:
- The isotonic concentration is approximately 0.4 mol/dm³ [1 mark].
- At this concentration, there is no net movement of water (0.0% change in mass), indicating the water potential of the solution equals the water potential of the potato cell sap [1 mark].
Marking notes: Accept 0.4 mol/dm³. Must explain that zero change in mass indicates equal water potentials.
Question 23 [10 marks]
(a) Describe the trend between 0°C and 40°C. [2 marks]
Answer:
- As temperature increases from 0°C to 40°C, enzyme activity increases [1 mark].
- The rate of increase is initially slow, then becomes more rapid, reaching a maximum at 40°C [1 mark].
Marking notes: Award 1 mark for stating activity increases, 1 mark for noting the maximum at 40°C or describing the shape.
(b) Explain the trend with reference to kinetic energy and enzyme-substrate complex formation. [3 marks]
Answer:
- As temperature increases, the kinetic energy of enzyme and substrate molecules increases [1 mark].
- This increases the frequency of collisions between enzyme and substrate molecules [1 mark].
- More enzyme-substrate complexes are formed per unit time, increasing the rate of reaction [1 mark].
Marking notes: Must mention kinetic energy, collision frequency, and enzyme-substrate complex formation.
(c) Explain why enzyme activity decreases above 40°C. [3 marks]
Answer:
- Above 40°C, the enzyme begins to denature [1 mark].
- High temperatures break the hydrogen bonds (and other bonds) that maintain the enzyme's specific three-dimensional / tertiary structure [1 mark].
- The active site loses its specific complementary shape, so the substrate can no longer bind / fit into the active site, and enzyme-substrate complexes cannot form [1 mark].
Marking notes: Must mention denaturation, bonds breaking, and active site shape change. Do not accept "enzyme is killed."
(d) State the optimum temperature for enzyme X. [1 mark]
Answer: 40°C [1 mark]
(e) Suggest why human enzymes and hot spring bacteria enzymes have different optimum temperatures. [1 mark]
Answer: Enzymes are adapted to the environmental temperatures in which the organism lives. Human enzymes function best at body temperature (37°C), while bacteria living in hot springs have evolved enzymes that are stable and function optimally at high temperatures. [1 mark]
Marking notes: Accept any reasonable explanation linking enzyme adaptation to the organism's environment.
Question 24 [10 marks]
(a) Identify food substance(s) in solution B. [1 mark]
Answer: Reducing sugar [1 mark]
Marking notes: Accept "glucose" or "reducing sugar." Do not accept just "sugar."
(b) Identify food substance(s) in solution C. [1 mark]
Answer: Starch [1 mark]
(c) Identify food substance(s) in solution D. [1 mark]
Answer: Protein [1 mark]
(d) State what the negative results for solution A indicate. [1 mark]
Answer: Solution A does not contain reducing sugar, starch, protein, or fats / Solution A contains none of the food substances tested for. [1 mark]
Marking notes: Accept "none of the above food substances are present."
(e) Explain why the conclusion that solution B contains both reducing sugar and starch is incorrect. [2 marks]
Answer:
- The iodine test for solution B gave a brown colour, which is a negative result [1 mark].
- If starch were present, the iodine test would have turned blue-black [1 mark].
Marking notes: Must reference the iodine test result and the expected positive result for starch.
(f) Describe how to carry out the ethanol emulsion test for fats. [4 marks]
Answer:
- Add about 2 cm³ of the food sample to a clean, dry test tube [1 mark].
- Add about 2 cm³ of ethanol to the test tube and shake thoroughly / vigorously to dissolve any fats present [1 mark].
- Pour the mixture into another test tube containing about 2 cm³ of water [1 mark].
- Observe: a cloudy white emulsion indicates the presence of fats / lipids [1 mark].
Marking notes: Award marks for: adding ethanol, shaking, adding water, and observing a cloudy white emulsion. Accept alternative wording if the essential steps are clear.
Section C: Free-Response Questions [20 marks]
Question 25 [10 marks]
(a) Describe the structure of an enzyme and explain how its structure is related to its function using the lock-and-key model. [5 marks]
Answer:
Structure:
- Enzymes are proteins made up of long chains of amino acids folded into a specific three-dimensional / tertiary structure [1 mark].
- The enzyme molecule has a specific region called the active site [1 mark].
Function and lock-and-key model:
- The active site has a specific shape that is complementary to the shape of the substrate molecule, like a lock and key [1 mark].
- The substrate molecule binds to the active site, forming an enzyme-substrate complex [1 mark].
- The reaction takes place, and products are formed and released, leaving the enzyme unchanged and able to catalyse another reaction [1 mark].
- The specificity of the active site means each enzyme can only catalyse one specific reaction / act on one specific substrate [1 mark].
Marking notes: Award up to 5 marks for clear explanation covering: protein nature, tertiary structure, active site, complementary shape, enzyme-substrate complex, specificity, and enzyme remaining unchanged. Maximum 5 marks.
(b) Describe how to investigate the effect of pH on amylase activity. [5 marks]
Answer:
Method:
- Prepare buffer solutions at different pH values (e.g., pH 4, 5, 6, 7, 8, 9) [1 mark].
- Place equal volumes of starch solution and buffer solution in test tubes, and add equal volumes of amylase solution [1 mark].
- Use a water bath to maintain a constant temperature (e.g., 37°C) throughout the investigation [1 mark].
- At regular time intervals, remove a sample and test with iodine solution on a white tile. Record the time taken for the iodine to no longer turn blue-black (indicating all starch has been broken down) [1 mark].
- Repeat the experiment at each pH and calculate the rate of reaction (1/time). Plot a graph of rate of reaction against pH to determine the optimum pH (where the rate is highest) [1 mark].
Controlled variables: Temperature, volume and concentration of starch solution, volume and concentration of amylase solution [1 mark].
Marking notes: Award marks for: using different pH buffers, controlling temperature with water bath, testing with iodine, recording time for starch breakdown, and plotting graph to find optimum. Maximum 5 marks.
Question 26 [10 marks]
(a) Distinguish between diffusion, osmosis, and active transport. [6 marks]
Answer:
Diffusion:
- Net movement of particles (molecules or ions) from a region of higher concentration to a region of lower concentration, down a concentration gradient [1 mark].
- Does not require energy (passive process) [0.5 mark].
- Examples: movement of oxygen, carbon dioxide, and dissolved substances [0.5 mark].
Osmosis:
- Net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane [1 mark].
- Does not require energy (passive process) [0.5 mark].
- Only involves water molecules [0.5 mark].
Active transport:
- Movement of molecules or ions from a region of lower concentration to a region of higher concentration, against a concentration gradient [1 mark].
- Requires energy from respiration (active process) [0.5 mark].
- Requires carrier proteins in the cell membrane [0.5 mark].
Marking notes: Award up to 6 marks. Must clearly distinguish all three processes in terms of direction, energy requirement, and substances involved. Accept a table format.
(b) Explain the importance of active transport in glucose absorption by the villi. [4 marks]
Answer:
- After a meal, the concentration of glucose in the small intestine may be lower than the concentration in the blood / epithelial cells of the villi [1 mark].
- Glucose cannot be absorbed by diffusion alone because the concentration gradient may not be favourable [1 mark].
- Active transport moves glucose from the lumen of the small intestine into the epithelial cells of the villi, against the concentration gradient [1 mark].
- This ensures that all glucose is absorbed from the digested food, even when the concentration in the intestine is low, maximising nutrient uptake [1 mark].
Marking notes: Must mention concentration gradient, active transport against the gradient, and the importance of complete absorption. Accept reference to carrier proteins and energy from respiration.
END OF ANSWER KEY