GCSE Biology Core Topics

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Part 1: Cell Biology and Organisation

Total for this section: 28 marks

1. Which statement correctly compares eukaryotic and prokaryotic cells? [2 marks]

Prokaryotic cells have a nucleus and eukaryotic cells do not.

Eukaryotic cells have a nucleus; prokaryotic cells do not.

Both types of cell always have chloroplasts.

Prokaryotic cells are always larger than eukaryotic cells.

2. Name the cell structure responsible for each function: [4 marks]

a) Controls the activities of the cell: ____________________

b) Site of aerobic respiration: ____________________

c) Makes proteins: ____________________

d) Controls movement of substances into and out of the cell: ____________________

3. An image of a cell is 36 mm wide. Its actual width is 0.12 mm. Calculate the magnification. Show your working. [3 marks]

4. Explain how each specialised cell is adapted to its function: [3 marks]

a) A sperm cell: ____________________________________________________________

b) A root hair cell: _________________________________________________________

5. Describe what happens during the cell cycle, including the importance of mitosis. [3 marks]

6. Complete the statements about movement of substances: [4 marks]

a) Diffusion is the net movement of particles from a ____________________ concentration to a ____________________ concentration.

b) Osmosis is the movement of ____________________ molecules through a partially permeable membrane.

c) Active transport requires energy released by ____________________ respiration.

7. An enzyme works fastest at pH 7. At pH 2 and pH 11, the reaction is much slower. Explain why. [4 marks]

8. Put these levels of organisation in order from smallest to largest: organ system, organ, cell, tissue. [2 marks]

____________________________________________________________________________

9. Explain how the digestive system uses enzymes to break down food. Include one named enzyme and its substrate. [4 marks]

10. The stomach is an organ. Explain why it is an organ rather than a tissue. [2 marks]

Part 2: Bioenergetics and Application

Total for this section: 34 marks

11. Complete the photosynthesis equations. [4 marks]

a) Word equation: carbon dioxide + ____________________ → glucose + ____________________

b) Symbol equation: 6CO₂ + 6H₂O → ____________________ + ____________________

12. A plant produces 18 bubbles of oxygen in two minutes at a low light intensity and 42 bubbles in two minutes at a higher light intensity. Give one conclusion and identify one possible limiting factor. [3 marks]

13. At a particular light intensity, a plant produces 42 bubbles of oxygen in two minutes. Calculate the rate in bubbles per minute. The rate then stays almost constant when light intensity increases. Suggest why. [3 marks]

14. Write the word equation for aerobic respiration. [2 marks]

____________________________________________________________________________

15. State the products of anaerobic respiration in animals and in yeast. [3 marks]

Animals: _________________________________________________________________

Yeast: __________________________________________________________________

16. Explain why a person continues breathing heavily after intense exercise. Use the term oxygen debt. [4 marks]

17. A potato cylinder has a mass of 25 g before being placed in a dilute sugar solution. Its final mass is 29 g. Calculate the percentage change in mass and explain the result. [3 marks]

18. In a sample of 90 cells, 18 are undergoing mitosis. Calculate the percentage of cells undergoing mitosis. [2 marks]

19. The reaction rates of an enzyme at pH 2, pH 7 and pH 9 are 4, 22 and 8 units respectively. Identify the optimum pH and explain the results at the other pH values. [3 marks]

20. During a sprint, muscles may respire anaerobically. Explain what happens in the muscles during and after the sprint. Include the substances produced and how the body repays the oxygen debt. [4 marks]

Total marks: 62

Answer Key — Separate Answer Pages

1. [2 marks] Eukaryotic cells have a nucleus; prokaryotic cells do not. Award 1 mark for each correct comparison.

2. [4 marks] a) Nucleus. b) Mitochondria. c) Ribosomes. d) Cell membrane.

3. [3 marks] Magnification = image size ÷ actual size. 36 ÷ 0.12 = 300×. Award marks for the correct formula, substitution and answer.

4. [3 marks] Sperm cell: has a flagellum for movement, many mitochondria for energy, and an acrosome containing enzymes. Root hair cell: has a long extension for a large surface area, a thin membrane, and many mitochondria for active transport. Award up to 2 marks for sperm and 1 mark for root hair, or equivalent valid adaptations.

5. [3 marks] The cell grows and increases sub-cellular structures; DNA is replicated; the nucleus divides by mitosis; the cell then divides into two genetically identical daughter cells. Award any three correct points.

6. [4 marks] a) Higher; lower. b) Water. c) Aerobic.

7. [4 marks] Enzymes have an optimum pH at which they work fastest. Extreme pH values change the shape of the active site. The substrate no longer fits, so fewer enzyme-substrate complexes form. The enzyme may become denatured.

8. [2 marks] Cell → tissue → organ → organ system.

9. [4 marks] Digestive enzymes break large, insoluble food molecules into small, soluble molecules that can be absorbed. For example, amylase breaks starch into sugars; protease breaks proteins into amino acids; lipase breaks lipids into fatty acids and glycerol. Award marks for the general explanation and a correct named enzyme-substrate pair.

10. [2 marks] An organ is made of different tissues working together to carry out a function. The stomach contains tissues such as muscle, glandular tissue and epithelial tissue.

11. [4 marks] a) Water; oxygen. b) C₆H₁₂O₆; 6O₂. Light and chlorophyll may be shown above the arrow but are not required for the four blanks.

12. [3 marks] Increasing light intensity increases the rate of photosynthesis, shown by more oxygen bubbles. A possible limiting factor is light intensity at the lower level, or carbon dioxide concentration or temperature at higher light intensity.

13. [3 marks] Rate = 42 ÷ 2 = 21 bubbles per minute. The plateau shows that light is no longer limiting; another factor, such as carbon dioxide concentration or temperature, limits the rate.

14. [2 marks] Glucose + oxygen → carbon dioxide + water. Energy is also released.

15. [3 marks] Animals: lactic acid. Yeast: ethanol and carbon dioxide. Award 1 mark for the animal product and 2 marks for both yeast products.

16. [4 marks] Anaerobic respiration produces lactic acid and does not release enough energy for continued intense activity. Extra oxygen is needed after exercise to break down or remove the lactic acid. Breathing and heart rate remain high to deliver this oxygen. This extra oxygen is the oxygen debt.

17. [3 marks] Change in mass = 29 − 25 = 4 g. Percentage change = 4 ÷ 25 × 100 = 16% increase. Water entered the potato cells by osmosis from the dilute solution because the water concentration was higher outside the cells.

18. [2 marks] Percentage = 18 ÷ 90 × 100 = 20%.

19. [3 marks] Optimum pH is pH 7. At pH 2 and pH 9, the active site changes shape, so fewer substrate molecules bind and the reaction rate decreases. Extreme pH can denature the enzyme.

20. [4 marks] During the sprint, muscles may lack enough oxygen and respire anaerobically. Glucose is converted to lactic acid, releasing a small amount of energy. After the sprint, breathing remains heavy to provide oxygen. The oxygen is used to break down or remove lactic acid and restore normal conditions, repaying the oxygen debt.

Indicative total: 62 marks