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Secondary 4 Pure Biology Preliminary Examination Paper 1

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TuitionGoWhere Practice Paper - Pure Biology Secondary 4

TuitionGoWhere Secondary School (AI)
PRELIMINARY EXAMINATION 2024
Version 1 of 5

Subject: Pure Biology
Level: Secondary 4
Paper: Topic Assessment – Cells and Biomolecules
Duration: 1 hour
Total Marks: 40

Name: __________________________
Class: __________
Date: ________________

Instructions to Candidates:

Write your name, class, and date in the spaces provided.
Answer all questions.
Write your answers in the spaces provided in this booklet.
The number of marks is given in brackets [ ] at the end of each question or part question.
You may use a calculator.

Section A: Multiple Choice Questions (10 Marks)

Answer all questions. For each question, there are four possible answers A, B, C, and D. Choose the one you consider correct.

1. Which of the following structures is found in both a typical plant cell and a typical animal cell?
A. Cell wall
B. Chloroplast
C. Mitochondrion
D. Large central vacuole
[1]

2. The diagram below shows an electron micrograph of a cell. Structure X is abundant in this cell.

Image pending generation for this question.

(Description: Structure X appears as small dark dots attached to membrane folds)
What is the primary function of Structure X?
A. Synthesis of lipids
B. Synthesis of proteins
C. Packaging of enzymes
D. Production of ATP
[1]

3. A student places a strip of potato tissue in a concentrated sugar solution. After 30 minutes, the potato strip becomes flexible and soft.
What explains this change?
A. Water entered the potato cells by osmosis, causing them to become turgid.
B. Water entered the potato cells by active transport, causing them to burst.
C. Water left the potato cells by osmosis, causing them to become flaccid.
D. Sugar entered the potato cells by diffusion, increasing their mass.
[1]

4. Which row correctly describes the movement of substances across a cell membrane?

	Diffusion	Osmosis	Active Transport
A	High to low concentration	High to low water potential	Low to high concentration
B	Low to high concentration	Low to high water potential	High to low concentration
C	High to low concentration	Low to high water potential	Low to high concentration
D	High to low concentration	High to low water potential	High to low concentration

[1]

5. Enzyme Q catalyses the breakdown of starch into maltose. The graph shows the rate of reaction at different temperatures.
(Description: Graph peaks at 37°C and drops to zero at 60°C)
Why does the rate of reaction drop to zero at 60°C?
A. The enzyme has been used up.
B. The substrate has been used up.
C. The enzyme has been denatured.
D. The activation energy has increased.
[1]

6. Which test and result correctly identifies the presence of protein in a food sample?
A. Benedict’s solution; blue to brick-red precipitate
B. Biuret solution; blue to purple/violet colour
C. Ethanol; clear solution to cloudy white emulsion
D. Iodine solution; brown to blue-black colour
[1]

7. Red blood cells are specialised for oxygen transport. Which feature is not an adaptation for this function?
A. Presence of a nucleus to control cell activities
B. Biconcave shape to increase surface area
C. Presence of haemoglobin to bind oxygen
D. Lack of mitochondria to prevent oxygen usage
[1]

8. A molecule is composed of glycerol and three fatty acid chains. It is insoluble in water.
What is this molecule?
A. Amino acid
B. Glucose
C. Triglyceride
D. Starch
[1]

9. In an experiment to investigate osmosis, dialysis tubing containing 10% sucrose solution is placed in a beaker of 5% sucrose solution.
What happens to the level of liquid inside the dialysis tubing after 1 hour?
A. It decreases because water moves out.
B. It decreases because sucrose moves out.
C. It increases because water moves in.
D. It increases because sucrose moves in.
[1]

10. Which statement about enzymes is correct?
A. Enzymes are carbohydrates that speed up chemical reactions.
B. Enzymes are destroyed during the reaction they catalyse.
C. Enzymes lower the activation energy of a reaction.
D. Enzymes work best at all pH levels.
[1]

Section B: Structured Questions (30 Marks)

Answer all questions in the spaces provided.

11. Fig. 11.1 shows a diagram of a root hair cell.

(Fig. 11.1: Diagram of a root hair cell with labels A, B, C, and D pointing to Cell Wall, Cell Membrane, Cytoplasm, and Nucleus respectively)

(a) Identify the structures labelled A and D.
A: _______________________________________________________ [1]
D: _______________________________________________________ [1]

(b) State one function of the structure labelled C.
_________________________________________________________________________ [1]

_________________________________________________________________________ [2]

(d) Root hair cells absorb mineral ions from the soil even when the concentration of ions in the soil is lower than in the cell sap.
(i) Name the process by which these ions are absorbed.
_______________________________________________________________________ [1]
(ii) State why this process requires energy.

_______________________________________________________________________ [1]

12. A student investigated the effect of pH on the activity of the enzyme amylase. The results are shown in Table 12.1.

Table 12.1

pH	Time taken for starch to disappear (seconds)
3	480
5	120
7	30
9	110
11	450

(a) Plot a graph of the time taken for starch to disappear against pH on the grid provided below.
(Grid provided with pH on x-axis 0-14 and Time on y-axis 0-500)
[4]

(b) From your graph, estimate the time taken for starch to disappear at pH 6.
____________________ seconds [1]

_________________________________________________________________________ [3]

(d) Suggest why the student kept the temperature constant at 35°C during the experiment.

_________________________________________________________________________ [1]

13. Fig. 13.1 shows a red blood cell placed in three different solutions: P, Q, and R.

(Fig. 13.1:
Solution P: Cell appears swollen/rounded (normal/turgid-like but animal cells don't have walls, so just normal biconcave or slightly swollen if hypotonic but not burst yet). Let's assume P is isotonic.
Solution Q: Cell appears shrivelled/crenated.
Solution R: Cell has burst/disappeared (ghost cell).)

Correction for standard O-Level context:
Solution P: Cell is normal (biconcave).
Solution Q: Cell is crenated (shrivelled).
Solution R: Cell has haemolysed (burst).

(a) Identify which solution (P, Q, or R) is:
(i) Hypertonic: _______________ [1]
(ii) Hypotonic: _______________ [1]

(b) Explain what happened to the red blood cell in solution Q.

_________________________________________________________________________ [3]

_________________________________________________________________________ [2]

14. Biological molecules are essential for life.

(a) Complete Table 14.1 by stating the basic units (monomers) and one main function for each biological molecule.

Table 14.1

Biological Molecule	Basic Unit (Monomer)	One Main Function
Protein	____________________	____________________
Starch	____________________	____________________
Fat (Lipid)	Glycerol and fatty acids	____________________

[3]

(b) Describe how you would test a sample of milk to confirm the presence of fat. Include the steps and the positive result.

_________________________________________________________________________ [3]

15. Fig. 15.1 shows a section of the human ileum wall.

(Fig. 15.1: Diagram showing villi)

(a) Name the structure shown in Fig. 15.1.
_________________________________________________________________________ [1]

(b) State two features of this structure that increase the rate of absorption of digested food.

_______________________________________________________________________ [2]

(c) Glucose is absorbed into the blood capillaries of the villus.
Explain how glucose moves from the lumen of the ileum into the epithelial cells against a concentration gradient.

_________________________________________________________________________ [3]

END OF PAPER

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Answers

TuitionGoWhere Practice Paper - Pure Biology Secondary 4

ANSWER KEY & MARKING SCHEME
Version 1 of 5

Section A: Multiple Choice Questions (10 Marks)

Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10
C	B	C	A	C	B	A	C	C	C

Explanations for tricky items:

Q1: Mitochondria are found in both. Cell walls, chloroplasts, and large vacuoles are plant-specific.
Q3: Concentrated sugar solution has lower water potential than potato cells. Water leaves cells by osmosis. Cells become flaccid.
Q4: Diffusion: High to low conc. Osmosis: High to low water potential. Active Transport: Low to high conc (against gradient).
Q7: RBCs do not have a nucleus. This provides more space for haemoglobin.
Q9: 10% sucrose (inside) has lower water potential than 5% sucrose (outside). Water moves from high WP (outside) to low WP (inside). Level rises.

Section B: Structured Questions (30 Marks)

11. Root Hair Cell

(a)
A: Cell wall [1]
D: Nucleus [1]

(b)
C is Cytoplasm.
Function: Site of metabolic reactions / contains enzymes / holds organelles in place. [1]
(Accept: Site of respiration if referring to cytoplasm generally, though mitochondria are specific. "Contains cell sap" is vacuole. Best answer: Site of chemical reactions.)

(c)

Long projection/hair increases surface area [1]
Increases the rate of osmosis/water absorption [1]

(d)
(i) Active transport [1]
(ii) Energy is required to move ions against the concentration gradient (from low to high concentration) [1]

12. Enzyme Activity and pH

(a) Graph Plotting [4]

1 mark: x-axis labelled "pH" with linear scale.
1 mark: y-axis labelled "Time taken (s)" with linear scale.
1 mark: All 5 points plotted correctly.
1 mark: Points joined with a smooth curve or straight lines (as per instruction, usually smooth curve for enzyme data, but straight lines are acceptable if specified. Standard is smooth curve for best fit).
(Note: If student plots Rate instead of Time, check if they inverted data. Question asks for Time. Graph should be U-shaped or V-shaped, minimum at pH 7.)

(b)
Approx. 60 seconds (Accept 50–70 seconds based on curve interpolation) [1]

(c)

At pH 3 and pH 11, the enzyme activity is very low (time taken is long) [1]
The extreme pH causes the enzyme (amylase) to denature [1]
The shape of the active site changes, so the substrate (starch) can no longer fit/bind [1]

(d)

To ensure that pH is the only variable affecting the rate of reaction / To control variables [1]
Temperature also affects enzyme activity; keeping it constant ensures fair test.

13. Osmosis in Red Blood Cells

(a)
(i) Q [1]
(ii) R [1]

(b)

Solution Q is hypertonic (lower water potential than the cell cytoplasm) [1]
Water moves out of the red blood cell by osmosis [1]
The cell loses water and shrinks/crenates [1]

(c)

Plant cells have a cell wall [1]
The cell wall is strong and rigid/inelastic, which prevents the cell from bursting when it becomes turgid [1]

14. Biological Molecules

(a) Table Completion [3]

Protein: Amino acids [1]; Growth and repair of tissues / Enzymes / Antibodies (Any one) [1]
Starch: Glucose [1]; Energy storage (in plants) [1]
Fat: (Given); Energy storage / Insulation / Protection of organs (Any one) [1]
(Note: 1 mark per row correct. If basic unit is wrong, function mark can still be awarded if consistent with the molecule named in the first column.)

(b) Fat Test (Emulsion Test) [3]

Add ethanol/alcohol to the sample and shake [1]
Pour the solution into water [1]
Positive result: A cloudy white emulsion forms [1]

15. Absorption in Ileum

(a)
Villus [1]

(b)
(Any two)

Thin wall (one cell thick) for short diffusion distance [1]
Rich blood supply (capillaries) to maintain concentration gradient [1]
Large surface area due to many villi/microvilli [1]

(c)

Process is active transport [1]
Requires energy (from respiration) [1]
Moves glucose against the concentration gradient (from low concentration in lumen to high concentration in cell) [1]

END OF MARKING SCHEME