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O Level Combined Science Life Sciences Quiz

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Questions

O-Level 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 is given in brackets [ ] at the end of each question or part question.
You may use a calculator.

Section A: Cell Biology and Movement of Substances (Questions 1–5)

1. Fig. 1.1 shows a diagram of a plant cell and an animal cell.

(Diagram description: Two cells side-by-side. Cell A has a rigid outer layer, a large central vacuole, and chloroplasts. Cell B has an irregular shape, no cell wall, and small vacuoles.)

(a) Identify which cell is the plant cell. [1]

(b) State one function of the structure labelled X (the large central vacuole) in the plant cell. [1]

2. A student investigated the effect of sucrose concentration on the mass of potato strips. The results are shown in Table 2.1.

Sucrose Concentration (mol/dm³)	Initial Mass (g)	Final Mass (g)	Change in Mass (g)
0.0	2.0	2.4	+0.4
0.2	2.0	2.2	+0.2
0.4	2.0	2.0	0.0
0.6	2.0	1.8	-0.2
0.8	2.0	1.6	-0.4

(a) Define the term osmosis. [2]

(b) Explain why the potato strip gained mass in the 0.0 mol/dm³ sucrose solution. [2]

3. Fig. 3.1 shows a section of the human small intestine villus.

(Diagram description: A finger-like projection with a central lacteal, capillaries, and a single layer of epithelial cells with microvilli.)

(a) Name the process by which glucose moves from the lumen of the intestine into the epithelial cells against a concentration gradient. [1]

(b) State two features of the villus that adapt it for efficient absorption. [2]

4. Enzymes are biological catalysts.

(a) Define the term enzyme. [1]

(b) Explain what happens to an enzyme when it is heated to 80°C. [2]

5. Active transport differs from diffusion.

(a) State one similarity between active transport and diffusion. [1]

(b) State one difference between active transport and diffusion. [1]

Section B: Human Physiology (Questions 6–12)

6. Fig. 6.1 shows the human digestive system.

(Diagram description: Labelled diagram showing mouth, oesophagus, stomach, liver, pancreas, small intestine, large intestine.)

(a) Name the organ that produces bile. [1]

(b) State the function of bile in digestion. [2]

7. Proteins are essential nutrients.

(a) Name the enzyme that breaks down proteins in the stomach. [1]

(b) State the end-product of protein digestion. [1]

8. Fig. 8.1 shows the human heart.

(Diagram description: Heart diagram with labels A (Right Atrium), B (Left Ventricle), C (Aorta), D (Vena Cava).)

(a) Name the blood vessel labelled C. [1]

(b) Explain why the wall of chamber B is thicker than the wall of chamber A. [2]

9. Blood contains different types of cells.

(a) State the function of red blood cells. [1]

(b) Explain how the structure of a red blood cell is adapted to its function. [2]

10. Respiration releases energy for cellular activities.

(a) Write the word equation for aerobic respiration. [2]

(b) State one use of the energy released during respiration in humans. [1]

11. During vigorous exercise, muscle cells may respire anaerobically.

(a) Write the word equation for anaerobic respiration in human muscle cells. [2]

(b) Explain why anaerobic respiration produces less energy than aerobic respiration. [1]

12. The excretory system removes waste products.

(a) Name the functional unit of the kidney. [1]

(b) State two substances found in healthy urine. [2]

Section C: Molecular Genetics and Ecology (Questions 13–20)

13. DNA carries genetic information.

(a) Name the two sugar-phosphate backbone components of a DNA nucleotide. [2]

(b) State the base pairing rule in DNA. [1]

14. Cell division ensures 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]

15. Fig. 15.1 shows a family pedigree for a genetic condition.

(Diagram description: Square (male) and Circle (female). Shaded shapes indicate affected individuals. Generation I: Unaffected male and female. Generation II: One affected female, two unaffected males.)

(a) Deduce whether the allele for this condition is dominant or recessive. Explain your answer. [2]

(b) Using A for the dominant allele and a for the recessive allele, state the genotype of the affected female in Generation II. [1]

16. Genetic engineering allows the production of human insulin.

(a) Name the enzyme used to cut the human insulin gene from DNA. [1]

(b) Name the structure used to insert the gene into a bacterial cell. [1]

17. Photosynthesis is vital for life on Earth.

(a) Write the balanced chemical equation for photosynthesis. [2]

(b) State two factors that limit the rate of photosynthesis. [2]

18. Fig. 18.1 shows a simple food chain: Grass → Rabbit → Fox.

(a) Identify the primary consumer in this food chain. [1]

(b) Explain why energy transfer between trophic levels is not 100% efficient. [2]

19. Carbon cycles through the ecosystem.

(a) Name the process by which plants remove carbon dioxide from the atmosphere. [1]

(b) Name the process by which decomposers release carbon dioxide into the atmosphere. [1]

20. Conservation of biodiversity is important.

(a) Define the term biodiversity. [1]

(b) State one human activity that threatens biodiversity. [1]

End of Quiz

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Answers

O-Level Combined Science Quiz - Life Sciences (Answer Key)

Total Marks: 40

Section A: Cell Biology and Movement of Substances

1. (a) Cell A [1] (b) Stores cell sap / maintains turgor pressure / supports the cell. [1] (c) Animal cells are heterotrophic / do not perform photosynthesis / do not contain chlorophyll. [1]

2. (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) [1] through a partially permeable membrane. (b) The sucrose solution had a higher water potential than the potato cell sap [1]. Water entered the potato cells by osmosis [1], causing them to gain mass. (c) 0.4 mol/dm³ [1]

3. (a) Active transport [1] (b) Any two of:

Large surface area due to microvilli [1]
Thin epithelium / one cell thick for short diffusion distance [1]
Rich blood supply / capillaries to maintain concentration gradient [1]
Lacteal present for absorption of fatty acids/glycerol [1]

4. (a) A biological catalyst / protein that speeds up chemical reactions without being used up. [1] (b) The enzyme denatures [1]. The shape of the active site changes [1], so the substrate can no longer bind.

5. (a) Both involve the movement of substances / molecules. [1] (b) Active transport requires energy (ATP) / moves against concentration gradient, whereas diffusion does not require energy / moves down concentration gradient. [1]

Section B: Human Physiology

6. (a) Liver [1] (b) Emulsifies fats [1] to increase surface area for lipase action [1]. (Also accepts: Neutralizes stomach acid).

7. (a) Pepsin [1] (b) Amino acids [1] (c) Add Biuret solution [1]. A colour change from blue to purple/violet indicates protein is present [1].

8. (a) Aorta [1] (b) Chamber B (Left Ventricle) pumps blood to the whole body / systemic circulation [1], which requires higher pressure than Chamber A (Right Atrium) which only pumps to the lungs / receives blood [1].

9. (a) Transport oxygen [1]. (b) Biconcave shape increases surface area for gas exchange [1]; No nucleus allows more space for haemoglobin [1].

10. (a) Glucose + Oxygen → Carbon Dioxide + Water (+ Energy) [2] (1 mark for correct reactants, 1 mark for correct products). (b) Muscle contraction / maintaining body temperature / active transport / synthesis of molecules. [1]

11. (a) Glucose → Lactic Acid (+ Energy) [2] (b) Glucose is not completely broken down / oxidation is incomplete [1].

12. (a) Nephron [1] (b) Any two of: Water, Urea, Salts/Ions. [2] (Do not accept glucose or protein for healthy urine).

Section C: Molecular Genetics and Ecology

13. (a) Deoxyribose (sugar) [1] and Phosphate (group) [1]. (b) Adenine pairs with Thymine; Guanine pairs with Cytosine. [1]

14. (a) Mitosis [1] (b) Growth / Repair of tissues / Asexual reproduction. [1]

15. (a) Recessive [1]. Unaffected parents (Generation I) produced an affected child (Generation II), meaning parents must be carriers [1]. (b) aa [1]

16. (a) Restriction enzyme [1] (b) Plasmid [1]

17. (a) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ [2] (1 mark for correct formulae, 1 mark for balancing). Light and Chlorophyll should be indicated above/below the arrow. (b) Light intensity, Carbon dioxide concentration, Temperature. [2] (Any two).

18. (a) Rabbit [1] (b) Energy is lost as heat / through respiration [1]; Energy is lost in waste / uneaten parts / excretion [1].

19. (a) Photosynthesis [1] (b) Respiration (by decomposers) / Decomposition. [1]

20. (a) The variety of species / organisms in an ecosystem / habitat. [1] (b) Deforestation / Pollution / Overhunting / Habitat destruction. [1]