Total marks: 80 · Duration: 75 minutes · Tier: Extended
Instructions to candidates
- Answer all questions.
- Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
- Write your answers in the spaces provided.
- You may use a calculator.
- Where a question describes a structure, a graph or an experiment in words, you may find it helpful to sketch it.
Information
- The total mark for this paper is 80.
- The number of marks for each question or part question is shown in brackets.
- This paper covers the Core and Supplement content of the Cambridge IGCSE Biology (0610) syllabus.
Paper
Question 1 — Classification and cells (10 marks)
(a) Give two features of all prokaryotic organisms. [2 marks]
(b) Explain why viruses are not placed in any of the five kingdoms. [1 mark]
(c) Explain how the sequences of bases in DNA are used to classify organisms. [2 marks]
(d) A mitochondrion is 2.0 μm long. In an electron micrograph, its image is 30 mm long. Calculate the magnification of the micrograph. [2 marks]
(e) Root hair cells contain many mitochondria. Explain why. [2 marks]
(f) Name the structure in a plant cell that contains cell sap. [1 mark]
Question 2 — Molecules, enzymes and movement of substances (11 marks)
(a) (i) One strand of a DNA molecule has the base sequence ATCGGA. Give the sequence of bases on the complementary strand. [1 mark]
(ii) State which bases pair with each other in DNA. [1 mark]
(b) Explain why an enzyme can catalyse only one type of reaction. [2 marks]
(c) Explain why the rate of an enzyme-catalysed reaction increases as the temperature rises from 10 °C to 30 °C. [2 marks]
(d) Plant tissue is placed in a concentrated sucrose solution. Explain, using the term water potential, what happens to the cells. [3 marks]
(e) A root is treated with a chemical that stops respiration. The uptake of mineral ions by the root stops. Explain why. [2 marks]
Question 3 — Plant nutrition and transport (12 marks)
(a) Write the balanced chemical equation for photosynthesis. [2 marks]
(b) A student measures the rate of photosynthesis of a plant at different light intensities and two concentrations of carbon dioxide.
- At 0.04% carbon dioxide, the rate rises as light intensity increases, then levels off at 20 arbitrary units.
- At 0.10% carbon dioxide, the rate rises as light intensity increases, then levels off at 35 arbitrary units.
(i) Explain why the rate levels off at 0.04% carbon dioxide. Use the data in your answer. [2 marks]
(ii) Explain why glasshouse growers sometimes increase the carbon dioxide concentration. [1 mark]
(c) Explain why a plant with a magnesium ion deficiency has yellow leaves. [1 mark]
(d) Explain the movement of sucrose in a plant in terms of sources and sinks. Give an example of each. [2 marks]
(e) Describe how water vapour is lost from a leaf. [3 marks]
(f) Explain why the rate of transpiration increases when the temperature increases. [1 mark]
Question 4 — Digestion, blood and immunity (12 marks)
(a) Explain two roles of hydrochloric acid in the stomach. [2 marks]
(b) Name the protease enzyme:
(i) secreted in the stomach [1 mark]
(ii) secreted by the pancreas. [1 mark]
(c) Explain how bile helps the digestion of fats. [2 marks]
(d) Describe how blood clots at a wound. [2 marks]
(e) (i) Explain the difference between active immunity and passive immunity. Give an example of each. [2 marks]
(ii) Explain why vaccination gives long-term protection against a disease. [2 marks]
Question 5 — Gas exchange, respiration and excretion (12 marks)
(a) Describe the changes in the chest that cause air to enter the lungs during inspiration. [3 marks]
(b) Write the balanced chemical equation for aerobic respiration. [2 marks]
(c) After a sprint, an athlete continues to breathe fast and deeply for several minutes. Explain why. [3 marks]
(d) Explain why glucose is not normally found in urine. [2 marks]
(e) Describe the role of the liver in deamination. [2 marks]
Question 6 — Coordination and response (12 marks)
(a) Describe how an impulse is transmitted across a synapse. [3 marks]
(b) Explain the role of glucagon in controlling the blood glucose concentration. [2 marks]
(c) Describe how the eye focuses on a near object. [3 marks]
(d) State the role of:
(i) FSH in the menstrual cycle [1 mark]
(ii) progesterone in the menstrual cycle. [1 mark]
(e) Explain why antibiotics kill bacteria but do not affect viruses. [2 marks]
Question 7 — Inheritance, ecosystems and biotechnology (11 marks)
(a) The ABO blood group alleles Iᴬ and Iᴮ are codominant, and both are dominant to Iᴼ. A woman with genotype IᴬIᴼ and a man with genotype IᴮIᴼ have a child.
Use a genetic diagram to show the possible blood groups of the child, and state the probability that the child has blood group O. [3 marks]
(b) Red–green colour blindness is caused by a recessive allele on the X chromosome. A woman who is a carrier (XᴮXᵇ) and a man with normal vision (XᴮY) have a son. State the probability that the son is colour-blind, and explain your answer. [2 marks]
(c) Describe the roles of nitrifying bacteria and denitrifying bacteria in the nitrogen cycle. [2 marks]
(d) Describe the roles of restriction enzymes and DNA ligase in genetic modification. [2 marks]
(e) State one use of:
(i) pectinase [1 mark]
(ii) lactase. [1 mark]