Cambridge A Level Biology 9700 — 2005 May/June Paper 2 · Variant 1

This document consists of 14 printed pages and 2 blank pages. SP (NF/CWG) S83423/3 © UCLES 2005 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level BIOLOGY 9700/02 Paper 2 Structured Questions AS May/June 2005 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name in the spaces provided at the top of this page. Write in dark blue or black pen in the spaces provided on the Question Paper. You may use a soft pencil for any diagrams, graphs, or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions. The number of marks is given in brackets [ ] at the end of each question or part question. Centre Number Candidate Number Name For Examiner’s Use 1 2 3 4 5 6 TOTAL

2 9700/02/M/J/05 Answer all the questions. 1 Fig. 1.1 shows the replication of one strand of a DNA double helix. Fig. 1.1 (a) Name W to Y. W … X … Y … [3] W X guanine Y For Examiner’s Use © UCLES 2005

3 9700/02/M/J/05 [Turn over (b) Explain how the structure of DNA enables it to replicate semi-conservatively. … … … … … … [3] (c) Explain why it is important that an exact copy of DNA is made during replication. … … … … [2] [Total: 8] For Examiner’s Use © UCLES 2005

4 9700/02/M/J/05 2 Fig. 2.1 is a drawing of a transverse section of a leaf. Fig. 2.1 (a) (i) Use label lines and the letters X, S, E and D to indicate the following on Fig. 2.1: X – a xylem vessel S – a phloem sieve tube E – a lower epidermal cell D – a palisade mesophyll cell [4] (ii) Calculate the magnification of Fig. 2.1. Show your working and express your answer to the nearest whole number. Answer … [2] 0.5 mm For Examiner’s Use © UCLES 2005

5 9700/02/M/J/05 [Turn over (b) Name two assimilates that move from the palisade mesophyll cells to the vascular tissue to be exported from the leaf. 1 … 2 … [2] (c) Explain, using the term water potential, how water moves from the vascular tissue to the atmosphere. … … … … … … … … [4] [Total: 12] For Examiner’s Use © UCLES 2005

6 9700/02/M/J/05 3 (a) As blood passes through the capillaries in the lungs it becomes oxygenated. Explain how the structure of haemoglobin aids the uptake of oxygen in the lungs. … … … … … … … … [4] Fig. 3.1 shows the dissociation curve of adult haemoglobin. Fig. 3.1 For Examiner’s Use © UCLES 2005 100 90 80 70 60 50 40 30 20 10 0 0 2 partial pressure of oxygen / kPa Percentage saturation of haemoglobin with oxygen 4 6 8 10 12 14

7 9700/02/M/J/05 [Turn over (b) Use the information given in Fig. 3.1 to complete the table below. [3] (c) During exercise the concentration of carbon dioxide in muscle tissue increases. This stimulates an increase in the release of oxygen from the blood. Explain how carbon dioxide stimulates the release of oxygen from the blood. … … … … … … [3] [Total: 10] For Examiner’s Use © UCLES 2005 part of the circulation partial pressure of percentage saturation oxygen / kPa of haemoglobin capillaries in the 98 lungs capillaries in muscle 70 tissue at rest capillaries in muscle tissue during 2.0 strenuous exercise

8 9700/02/M/J/05 4 Collagen is found in the extracellular matrix of muscles, tendons, ligaments and bones. Fibroblast cells in these tissues make collagen by synthesising polypeptides that form molecules with a triple helix shape. These are secreted from fibroblasts into the extracellular matrix where enzymes assemble them into collagen fibres. Fig. 4.1 is a diagram summarising these events. Fig. 4.1 (a) (i) Name the processes occurring at A, B and C. A … B … C … [3] For Examiner’s Use © UCLES 2005 fibroblast cell extracellular matrix triple helix molecules being assembled into collagen fibres endoplasmic reticulum DNA A F E B D C not drawn to scale cytoplasm nucleus

9 9700/02/M/J/05 [Turn over (ii) Name structures D and E. D … E … [2] (iii) Name molecule F. F … [1] Collagen is continuously broken down in the extracellular matrix by the enzyme collagenase, which catalyses the hydrolysis of the peptide bond between the amino acids glycine and isoleucine. (b) Suggest how collagenase is only able to act on the peptide bond between glycine and isoleucine and not on peptide bonds between any other amino acids. … … … … [2] (c) Draw a diagram below to show how the peptide bond between glycine and isoleucine is broken by hydrolysis including the product or products. [3] [Total: 11] N C C N C H O H CH CH3 CH2 CH3 H H O C For Examiner’s Use © UCLES 2005

10 9700/02/M/J/05 5 The eelgrass, Zostera, is a marine plant that forms dense vegetation in shallow coastal waters. The primary consumers in this ecosystem eat the eelgrass and the photosynthetic algae that grow on its surface. Fig. 5.1 shows the flow of energy through an eelgrass ecosystem. The figures in circles represent the energy transfer in kJ m–2 yr–1. Fig. 5.1 carnivorous birds invertebrate predators, e.g. crabs fish 2.5 42 detritus feeders, suspension feeders, grazers 42 400 1.05 x 106 eelgrass and photosynthetic algae sunlight dead plants and animals from other ecosystems 409 For Examiner’s Use © UCLES 2005

11 9700/02/M/J/05 [Turn over (a) Calculate the percentage of energy transferred from primary consumers to the secondary consumers in the ecosystem shown in Fig. 5.1. Show your working and express your answer to the nearest whole number. Answer …………………… [2] (b) Explain why little of the energy present in producers is transferred to the secondary consumers. … … … … … … … … [4] (c) Dead plants contain nitrogen in the form of proteins. These are decomposed by bacteria. Outline how bacteria convert nitrogen in these proteins to a form that may be taken up by living plants. … … … … [2] [Total: 8] For Examiner’s Use © UCLES 2005

12 9700/02/M/J/05 6 (a) Substances are exchanged between the plasma, tissue fluid, lymph and red blood cells. Complete the table below to show which of the statements apply to each of these components of the body. Fill in each box using a tick (✓) to show that the statement applies or a cross (✗) if it does not. The first row has been completed for you. [4] (b) Nicotine is the drug in tobacco smoke. State two effects of nicotine on the cardiovascular system. … … … … [2] For Examiner’s Use © UCLES 2005 cytoplasm statement plasma tissue fluid lymph of red blood cells formed by leakage from capillaries ✗ ✔ ✗ ✗ contains haemoglobin contains water contains antibodies in direct contact with muscle cells

13 9700/02/M/J/05 [Turn over Table 6.1 shows information on smoking and lung cancer in six countries. Table 6.1 shows: • the percentage of male and female adults who smoke regularly in each country; • the death rates from lung cancer expressed as deaths per 100 000 of the population of each country. Table 6.1 (c) Explain whether or not there is any evidence in Table 6.1 to support the following statements. Use the data in the table to support your answer. Men are more at risk of dying from lung cancer than women. … … … Countries where a high percentage of the population smoke have high death rates from lung cancer. … … … [3] For Examiner’s Use © UCLES 2005 percentage of the deaths from lung cancer / country population who smoke deaths per 100 000 males females males females China 53.4 4.0 22.7 10.5 France 33.0 21.0 73.3 14.4 Malaysia 49.2 3.5 5.6 2.3 New Zealand 25.1 24.8 47.3 29.2 South Africa 43.8 11.7 13.8 5.4 Trinidad and Tobago 42.1 8.0 12.3 4.2

14 9700/02/M/J/05 (d) Table 6.1 shows that a larger percentage of men in some countries, such as Malaysia, smoke compared with New Zealand. It also shows that the death rate from lung cancer for men in Malaysia is much lower. Suggest two other pieces of information about men who smoke that would be useful in evaluating the risks of developing lung cancer. 1 … … 2 … … [2] [Total: 11] For Examiner’s Use © UCLES 2005

16 9700/02/M/J/05 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary and Advanced Level MARK SCHEME for the June 2005 question paper 9700 BIOLOGY 9700/02 Paper 2 (Structured Questions AS), maximum mark 60 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. This shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the June 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Grade thresholds for Syllabus 9700 (Biology) in the June 2005 examination. minimum mark required for grade: maximum mark available A B E Component 2 60 44 39 25 The thresholds (minimum marks) for Grades C and D are normally set by dividing the mark range between the B and the E thresholds into three. For example, if the difference between the B and the E threshold is 24 marks, the C threshold is set 8 marks below the B threshold and the D threshold is set another 8 marks down. If dividing the interval by three results in a fraction of a mark, then the threshold is normally rounded down.

June 2005 GCE A AND AS LEVEL MARK SCHEME MAXIMUM MARK: 60 SYLLABUS/COMPONENT: 9700/02 BIOLOGY Paper 2 (Structured Questions AS)

Page 1 Mark Scheme Syllabus Paper GCE A/AS Level – JUNE 2005 9700 2 © University of Cambridge International Examinations 2005 Question Expected Answers Marks 1 (a) W X Y cytosine; deoxyribose; nucleotide (triphosphate); [3] (b) base pairing/A-T and C-G; A purine - pyrimidine ref to complementary/explained with ref to H bonds; R complementary in wrong context (free) nucleotides pair with both, strands/each strand/polynucleotides/sides; both strands act as templates; to produce two DNA molecules that are identical to one another; [max 3] (c) (all nuclei/cells) are genetically identical; A genetic stability, same genetic information, exact genetic material, genetic material does not vary, same genotype; no mutation; any consequence of mutation; e.g. cells not recognised, cells divide uncontrollably, substitution of 1 amino acid results in disease e.g. sickle cell anaemia, enzyme’s active site altered, forms different protein with different function. [max 2] [Total: 8]

Page 2 Mark Scheme Syllabus Paper GCE A/AS Level – JUNE 2005 9700 2 © University of Cambridge International Examinations 2005 Question Expected Answers Marks 2 (a) (i) X to xylem vessel; S to phloem sieve tube element; R companion cell E to lower epidermal cell; (including guard cells) R cuticle D to palisade mesophyll cell; [4] (ii) Award 1 mark for correct working; Award 1 mark for correct answer; Expect 120/0.5 = 240 A 119 - 121/0.5 = 238 - 242 or any working that gives the correct answer R all others, [2] (b) sucrose; amino acids; A two named amino acids for two marks [2] (c) lower/more negative, water potential; A ref to water potential gradient/xylem has a higher water potential R less water potential (of) spongy mesophyll cell/tissue; R leaf cells large surface area/many cell walls(of spongy mesophyll cells); (moves through) through cell walls/surfaces; R ref to appoplast/symplast evaporation of water; from spongy mesophyll cell walls; into (substomatal/intercellular) air space; diffusion of water vapour; through stomata; [max 4] [Total: 12]

Page 3 Mark Scheme Syllabus Paper GCE A/AS Level – JUNE 2005 9700 2 © University of Cambridge International Examinations 2005 Question Expected Answers Marks 3 (a) 4 polypeptides/4 globins/4 amino acid chains; outwardly pointing hydrophilic (R) groups, maintain solubility/AW; each with a haem group; ref to iron/Fe2+ ( ion); R Fe3+/iron atom temporary attachment to oxygen; A readily attaches/binds combines with R oxygen binds to haem 4 molecules of oxygen; A 4 O2/8 oxygen atoms R 4 oxygens unqualified oxyhaemoglobin; A HbO8 ref to cooperative binding; [max 4] (b) part of the circulation partial pressure of oxygen/kPa % saturation of haemoglobin capillaries in the lungs accept answers between 12 and 14; capillaries in muscle tissue at rest 5; capillaries in muscle tissue during strenuous exercise 20; [3] (c) carbon dioxide reacts with water to form carbonic acid; catalysed by carbonic anhydrase; dissociates to hydrogen carbonate and hydrogen ions; hydrogen ions combine with haemoglobin; R hydrogen ions replace oxygen in haemoglobin forms haemoglobinic acid/HHb; so releasing oxygen; ignore ref to Bohr shift (question says ‘explain’) A from equations. [max 3] [Total: 10]

Page 4 Mark Scheme Syllabus Paper GCE A/AS Level – JUNE 2005 9700 2 © University of Cambridge International Examinations 2005 Question Expected Answers Marks 4 (a) (i) A B C transcription; (ignore mRNA synthesis) translation; exocytosis; R secretion [max 3] (ii) D E (sub unit of) ribosome Golgi apparatus/body; [2] (iii) F mRNA; [1] (b) active site; (is) specific shape; A complementary/other amino acids are the wrong shape to fit, R same shape only accepts R groups of these two amino acids; R accepts peptide bond [2] (c) correct bond broken (between C-N); involvement of water molecule in breaking the peptide bond shown clearly; two amino acids with free groups as follows -COOH/-COO- and -NH2/-NH3 +; A from diagram(s). [3] [Total: 11]

Page 5 Mark Scheme Syllabus Paper GCE A/AS Level – JUNE 2005 9700 2 © University of Cambridge International Examinations 2005 Question Expected Answers Marks 5 (a) 1 mark for working 86.5/809 x 100 ( = 10.69); A 42 + 42 + 2.5/400 + 409 x 100 R 42/400 x 100 = 10.5 = 11 1 mark for correct answer 11%; R 10.7/other units if specified [2] (b) Energy losses in respiration; R used up in/needed in respiration, energy lost in movement waste/urine/faeces/dead parts/excreta/excretion; primary consumers do not eat all the plant matter; A for secondary consumers not all parts of, plants/primary consumers, are digestible; energy losses as heat qualified e.g. in digestive system (of consumers)/to environment/atmosphere/surroundings; plants/primary consumers, migrate/swept away, by tide/waves AW; energy losses to decomposers; [max 4] (c) proteins
amino acids; A proteins are decayed into amino acids deamination; ammonification/ammonia/ammonium ion; ammonia/ammonium ions, to nitrate; A nitrification oxidation; [max 2] [Total: 8]

Page 6 Mark Scheme Syllabus Paper GCE A/AS Level – JUNE 2005 9700 2 © University of Cambridge International Examinations 2005 Question Expected Answers Marks 6 (a) one mark per row, do not penalise where crosses are omitted Statement plasma tissue fluid lymph cytoplasm of red blood cells contains haemoglobin     contains water     contains antibodies     in direct contact with muscle cells     [4] (b) increases heart rate; increases blood pressure; constricts, arterioles/arteries; A narrows diameter/lumen R ref to blood vessels reduces blood flow to, periphery/hands/fingers/AW; increases ‘stickiness’ of platelets; R blood cells ref to atheroma, plaque, atherosclerosis, cardiovascular disease, damage to endothelium; Generally, mark 1st 2 sentences (look for full stops!). However if 2 correct points in 1st sentence allow this. [max 2] (c) mark two parts together (in every country) the death rate for men is higher than that for women; R ref to % of death in some countries where many people smoke there are low death rates from lung cancer; data quote to support either part; Here we need to be very precise! We can accept male or female data quoted in the correct context. R any ‘ADDITIVE %s’!/incorrect units. [max 3]

Page 7 Mark Scheme Syllabus Paper GCE A/AS Level – JUNE 2005 9700 2 © University of Cambridge International Examinations 2005 (d) age; how long men have been smoking/age at which start smoking; how many cigarettes are smoked per day; A heavy/light smokers any 2 risk factors that are linked with lung cancer;; e.g. Hereditary/running in families; working environment (pollution/passive smoking/exposure to other carcinogens/radiation); type of cigarette(tar levels/cigars/cigarettes smoked/brand of cigarette/whether filtered/unfiltered); depth of inhalation; R refs to diet/alcohol/lifestyle/stress. [max 2] [Total: 11]