Total marks: 80 · Duration: 105 minutes · Tier: Higher
Instructions to candidates
- Use black ink or black ball-point pen.
- Answer all questions.
- Write your answers in the spaces provided.
- In calculations, show your working and give the unit of your answer.
- You may use a calculator.
- Where a question describes apparatus, a graph or a diagram in words, you may find it helpful to sketch it.
Information
- The total mark for this paper is 80.
- The number of marks is given in brackets at the end of each question or part-question.
- Questions marked with an asterisk (*) assess the quality of extended response (QER): your answer should be clear, logical and use correct scientific terms.
- This paper covers WJEC GCSE Biology Unit 1 (Cells, Organ Systems and Ecosystems), Higher Tier: cells and movement across membranes; respiration and the respiratory system; digestion; the circulatory system; plants and photosynthesis; and ecosystems, nutrient cycles and human impact.
Paper
Question 1 — Cells and movement across membranes (10 marks)
(a) State the function of the cell membrane and of the mitochondria. [2 marks]
(b) A drawing of a cell is 24 mm long. The magnification of the drawing is ×800. Calculate the real length of the cell in micrometres (μm). [2 marks]
(c) Explain why active transport can only take place in living cells. [2 marks]
(d) Define osmosis. [2 marks]
(e) Describe and explain what happens to a plant cell placed in a concentrated sugar solution. [2 marks]
Question 2 — Enzymes (10 marks)
A student investigates the effect of temperature on the enzyme trypsin, which digests the protein in milk. As the protein is digested, the cloudy milk becomes clear. The student records the time taken for the milk to clear.
| Temperature (°C) | 20 | 30 | 40 | 50 | 60 |
|---|---|---|---|---|---|
| Time taken to clear (s) | 300 | 150 | 90 | 200 | did not clear |
(a) Calculate the rate of reaction at 40 °C, using rate = 1000 ÷ time. [1 mark]
(b) Explain why the rate increases from 20 °C to 40 °C. [2 marks]
(c) Explain why the milk did not clear at 60 °C. [2 marks]
(d) Give two variables the student should keep constant. [2 marks]
(e) Suggest how the student could find the optimum temperature more precisely. [1 mark]
(f) Explain why trypsin digests proteins but not starch. [2 marks]
Question 3 — Respiration and the respiratory system (10 marks)
(a) Write the word equation for aerobic respiration. [1 mark]
(b) Give two uses of the energy released by respiration in the human body. [2 marks]
(c) Describe how air is drawn into the lungs during breathing in. [3 marks]
(d) During a sprint, a runner's muscles respire anaerobically. Explain why the runner continues to breathe deeply after the sprint has ended. [2 marks]
(e) Explain how smoking damages the lining of the airways. [2 marks]
Question 4 — Digestion (10 marks)
A student sets up a model of the gut. A bag of Visking tubing is filled with a mixture of starch solution and amylase and placed in a test tube of water at 37 °C. After 30 minutes, the water around the bag is tested. It gives a positive result with Benedict's solution and a negative result with iodine solution.
(a) Explain these results. [3 marks]
(b) State which part of the gut the Visking tubing represents. [1 mark]
(c) Explain why the model is kept at 37 °C. [1 mark]
(d) Describe two ways in which villi are adapted for absorption. [2 marks]
(e) Describe two roles of bile in digestion. [2 marks]
(f) Name the products of the digestion of protein. [1 mark]
Question 5 — The circulatory system (10 marks)
(a)* Describe the route that blood takes through the heart and lungs, starting from the vena cava, and explain how the structure of the heart is adapted to its function. [6 marks]
(b) Explain two ways in which capillaries are adapted for exchanging substances with body cells. [2 marks]
(c) Explain how a build-up of fatty deposits in the coronary arteries can cause a heart attack. [2 marks]
Question 6 — Photosynthesis (10 marks)
(a) Write the balanced symbol equation for photosynthesis. [2 marks]
(b) Describe three ways in which a leaf is adapted for photosynthesis. [3 marks]
(c) A student measures the rate of photosynthesis of pondweed at different light intensities. Above a certain light intensity, the rate stays the same. When the student adds more sodium hydrogencarbonate to the water, the rate increases further.
Explain these results. [2 marks]
(d) Explain why sodium hydrogencarbonate is added to the water at the start of the experiment. [1 mark]
(e) Give two uses of the glucose made in photosynthesis. [2 marks]
Question 7 — Transport in plants (10 marks)
(a) A student uses a potometer to measure the rate of water uptake by a leafy shoot. An air bubble moves 60 mm along the capillary tube in 5 minutes. The cross-sectional area of the capillary tube is 0.8 mm².
Calculate the rate of water uptake in mm³ per minute. [2 marks]
(b) State one assumption the student makes when using the potometer to measure the rate of transpiration. [1 mark]
(c) Explain how increasing the humidity of the air affects the rate of transpiration. [2 marks]
(d) Give two differences between xylem and phloem. [2 marks]
(e) Describe the symptoms of a plant that lacks:
(i) nitrates [1 mark]
(ii) magnesium. [1 mark]
(f) Name the process by which root hair cells absorb mineral ions from the soil. [1 mark]
Question 8 — Ecosystems, nutrient cycles and human impact (10 marks)
(a)* Describe the roles of microorganisms in the nitrogen cycle, and explain why farmers may need to add nitrogen fertilisers to fields where crops are harvested. [6 marks]
(b) Lichens are used as indicator species for air pollution. Explain how lichens can show the level of sulfur dioxide in the air. [2 marks]
(c) In a food chain, the primary consumers receive 1500 kJ/m² per year and the secondary consumers receive 120 kJ/m² per year. Calculate the percentage efficiency of energy transfer between these two trophic levels. [2 marks]