Total marks: 90 · Duration: 105 minutes · Tier: Higher
Instructions to candidates
- Use black ink. You may use an HB pencil for graphs and diagrams.
- Answer all the questions.
- In calculations, show your working and give the unit of your answer.
- You may use a scientific or graphical calculator.
- Section A: for each question, choose one answer, A, B, C or D.
- 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 90. Section A is worth 15 marks and Section B is worth 75 marks.
- The marks for each question are shown in brackets.
- Quality of extended response will be assessed in questions marked with an asterisk (*).
- This paper covers OCR GCSE (9–1) Gateway Biology A Higher Paper 1 content, topics B1 to B3: cell level systems; scaling up; and organism level systems.
Paper
Section A — Multiple choice (15 marks)
1. Which sub-cellular structure contains the enzymes for aerobic respiration? [1 mark]
A ribosome B nucleus C mitochondrion D chloroplast
2. What is meant by the resolution of a microscope? [1 mark]
A the ability to distinguish between two points that are close together B the number of times an image is enlarged C the brightness of the image D the size of the field of view
3. Which bases pair together in a DNA molecule? [1 mark]
A adenine and guanine B adenine and thymine C cytosine and thymine D guanine and uracil
4. Why does an enzyme stop working at a very high temperature? [1 mark]
A it has been used up B its molecules move too slowly C the substrate is denatured D the shape of its active site has changed
5. Which are the products of anaerobic respiration in yeast? [1 mark]
A ethanol and carbon dioxide B lactic acid only C carbon dioxide and water D lactic acid and carbon dioxide
6. Which statement about photosynthesis is correct? [1 mark]
A it releases energy to the surroundings B it takes place in the mitochondria C it is an endothermic reaction D it produces carbon dioxide
7. A lamp is moved from 10 cm to 20 cm away from a plant. By what factor does the light intensity at the plant change? [1 mark]
A it halves B it falls to one quarter C it doubles D it falls to one tenth
8. What does mitosis produce? [1 mark]
A four genetically different cells B two genetically different haploid cells C four identical haploid cells D two genetically identical diploid cells
9. Where are stem cells found in plants? [1 mark]
A meristems B xylem C phloem D guard cells
10. What is the surface area to volume ratio of a cube with sides of 3 cm? [1 mark]
A 1 : 1 B 3 : 1 C 2 : 1 D 6 : 1
11. Which type of blood vessel has the thickest layer of muscle and elastic fibres? [1 mark]
A capillary B artery C vein D venule
12. In which tissue does translocation take place? [1 mark]
A xylem B palisade mesophyll C epidermis D phloem
13. Which part of the brain coordinates movement and balance? [1 mark]
A cerebellum B medulla C cerebral cortex D hypothalamus
14. Which hormone causes an egg to mature in the ovary? [1 mark]
A progesterone B LH C FSH D oestrogen
15. Which hormone causes the blood glucose concentration to rise? [1 mark]
A insulin B glucagon C ADH D thyroxine
Section B (75 marks)
Question 16 — Cells and microscopy (10 marks)
(a) Give two differences between prokaryotic cells and eukaryotic cells. [2 marks]
(b) In a micrograph, a cell is 36 mm wide. The magnification is ×1200. Calculate the real width of the cell in metres. Give your answer in standard form. [3 marks]
(c) Explain why stains are used when viewing cells with a light microscope. [1 mark]
(d) Give one advantage of a light microscope over an electron microscope. [1 mark]
(e) Explain how the development of the electron microscope increased our understanding of sub-cellular structures. [2 marks]
(f) Name the sub-cellular structure where photosynthesis takes place. [1 mark]
Question 17 — DNA, protein synthesis and enzymes (11 marks)
(a) (i) DNA is a polymer. Name the monomers that make up DNA. [1 mark]
(ii) Describe the structure of one of these monomers. [2 marks]
(b) Describe how a protein is made from the information in a gene. [4 marks]
(c) A student adds catalase to hydrogen peroxide and collects 24 cm³ of oxygen in the first 30 seconds. Calculate the mean rate of reaction in cm³/s. [2 marks]
(d) The student repeats the experiment with more concentrated hydrogen peroxide. Explain why the rate increases at first but stops increasing at high concentrations. [2 marks]
Question 18 — Respiration and photosynthesis (12 marks)
(a) Give two differences between aerobic and anaerobic respiration in humans. [2 marks]
(b) Explain why aerobic respiration transfers more energy per molecule of glucose than anaerobic respiration. [2 marks]
(c) Write the balanced symbol equation for photosynthesis. [2 marks]
(d) A student measures the rate of photosynthesis of pondweed at different carbon dioxide concentrations, at 20 °C and at 30 °C. At both temperatures, the rate rises as the carbon dioxide concentration increases and then levels off. The rate levels off at a higher value at 30 °C.
(i) Explain why the rate levels off at 20 °C. [2 marks]
(ii) Explain why the rate of photosynthesis falls if the temperature rises above about 45 °C. [2 marks]
(e) Explain why photosynthesis is described as an endothermic reaction. [1 mark]
(f) Suggest how the student could measure the rate of photosynthesis of the pondweed. [1 mark]
Question 19 — Supplying the cell (10 marks)
(a) A potato cylinder has a mass of 5.20 g. After 30 minutes in distilled water, its mass is 5.72 g. Calculate the percentage change in mass. [2 marks]
(b) Explain why the mass of the cylinder increased. [2 marks]
(c) Explain why glucose is absorbed from the small intestine by active transport, as well as by diffusion. [2 marks]
(d) Describe what happens in a cell before it divides by mitosis. [2 marks]
(e) Give one potential benefit and one risk of using stem cells in medicine. [2 marks]
Question 20 — Exchange and transport (12 marks)
(a)* Explain how water moves from the soil, through a plant, and out into the air, and describe how light intensity, temperature, humidity and air movement affect the rate of transpiration. [6 marks]
(b) Explain two ways in which the alveoli are adapted for efficient gas exchange. [2 marks]
(c) Explain two ways in which red blood cells are adapted to carry oxygen. [2 marks]
(d) Describe two differences between the structure of an artery and the structure of a vein. [2 marks]
Question 21 — The nervous system (10 marks)
(a) A person touches a hot object and pulls their hand away. Describe the pathway of this reflex arc. [3 marks]
(b) Explain how a nerve impulse passes across a synapse. [2 marks]
(c) Describe the cause of short sight (myopia) and how it can be corrected. [2 marks]
(d) Describe one method scientists use to study the function of different regions of the brain. [1 mark]
(e) State the function of:
(i) the cerebral cortex [1 mark]
(ii) the medulla. [1 mark]
Question 22 — Hormones and homeostasis (10 marks)
(a)* Explain how hormones are used both in contraception and in treating infertility. [6 marks]
(b) Explain how the body responds when the blood glucose concentration rises after a meal. [2 marks]
(c) Give one way of treating Type 2 diabetes. [1 mark]
(d) What is meant by negative feedback? [1 mark]