Cambridge A Level Biology 9700 — 2014 May/June Paper 2 · Variant 1

This document consists of 11 printed pages and 1 blank page. DC (LK/CGW) 79170/3 © UCLES 2014 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 7 8 6 0 9 0 8 1 9 5 * BIOLOGY 9700/21 Paper 2 Structured Questions AS May/June 2014 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 ink. You may use a soft pencil for any diagrams, graphs, or rough working. Do not use red ink, staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

2 9700/21/M/J/14 © UCLES 2014 Answer all the questions. 1 Vibrio cholerae is a prokaryotic organism. Fig. 1.1 shows the structure of a cell of V. cholerae. 3.0 +m G F E D C A B capsule Fig. 1.1 (a) Calculate the magnification of Fig. 1.1. Show your working and give your answer to the nearest whole number. magnification × … [2] (b) Locate the structures in Fig. 1.1 that apply to each of the features shown in Table 1.1. Complete Table 1.1 by writing the appropriate letter and the name of the structure. You must only give one letter in each case. You may use each letter once, more than once or not at all. The first answer has been completed for you. Table 1.1 feature identity name provides motility F flagellum stores genetic information partially permeable composed of murein (peptidoglycan) site of translation [4]

3 9700/21/M/J/14 © UCLES 2014 [Turn over (c) State three structural features that are present in a mesophyll cell in a leaf that are not present in a prokaryotic cell such as that of V. cholerae. 1. … 2. … 3. … [3] (d) Describe how V. cholerae is transmitted from an infected person to an uninfected person. … … … … … [2] (e) It is important to know how pathogens are transmitted in order to develop effective control methods. Explain how this knowledge is used to control the spread of V. cholerae in the human population. … … … … … … … [3] [Total: 14]

4 9700/21/M/J/14 © UCLES 2014 2 Azolla filiculoides is an aquatic fern that floats on the surface of lakes. The nitrogen-fixing microorganism, Anabaena azollae, lives within the leaves of the fern. The beetle, Stenopelmus rufinasus, feeds on A.filiculoides. (a) State the ecological terms applied to each of the following descriptions of these species. description ecological term all the members of the species A. filiculoides floating on a lake all the organisms, including A. filiculoides, A. azollae and S. rufinasus, found living in and on the lake organisms, such as A. filiculoides, that absorb light energy, fix carbon dioxide and make organic compounds available to animals that eat them the role of species, such as A. filiculoides, A. azollae and S. rufinasus, in the lake ecosystem [4] (b) Explain the importance of nitrogen-fixing organisms, such as A. azollae, in ecosystems. … … … … … … …[3] [Total: 7]

5 9700/21/M/J/14 © UCLES 2014 [Turn over 3 Starch is composed of two polysaccharides, amylose and amylopectin. Fig. 3.1 shows a molecule of α-glucose before being added to the end of a molecule of amylose. H CH2OH OH H OH H H H O … O H CH2OH OH H OH H H H O O H CH2OH OH H OH OH H H H O H CH2OH OH H OH OH HO H H H O O Fig. 3.1 (a) (i) Complete Fig. 3.1 to show how a molecule of α-glucose is added to the amylose. [3] (ii) Name the bond that forms between glucose molecules in polysaccharides, such as amylose. …[1] (b) Glycogen and cellulose are two other polysaccharides. Complete Table 3.1 to compare glycogen and cellulose with amylose. Table 3.1 feature amylose glycogen cellulose monomer α-glucose branched or unbranched molecule unbranched role in organisms energy storage [3]

6 9700/21/M/J/14 © UCLES 2014 (c) Type 2 diabetes (insulin-independent diabetes) is a non-infectious disease. If not treated, this disease is characterised by large fluctuations in the concentration of glucose in the blood. Maltase is an enzyme that completes the digestion of starch in humans. Molecules of maltase are bound to the microvilli of epithelial cells in the small intestine. Ascorbase is a drug used in the treatment of type 2 diabetes. Molecules of ascorbase have a very similar shape to that of the substrate for maltase. (i) Explain how ascorbase acts to inhibit these membrane-bound enzymes. … … … … … … … [3] (ii) Suggest why ascorbase can be used to treat people who have type 2 diabetes. … … … … … … [2] [Total: 12]

7 9700/21/M/J/14 © UCLES 2014 [Turn over 4 B-lymphocytes respond to the presence of a non-self antigen by dividing as shown in Fig. 4.1. B-lymphocyte non-self antigen cells R cells P Fig. 4.1 (a) (i) Explain what is meant by the term non-self antigen. … … … … … [2] (ii) Outline how B-lymphocytes recognise non-self antigens. … … … … … [2]

8 9700/21/M/J/14 © UCLES 2014 The cells labelled P on Fig. 4.1 continue to divide to give rise to many cells that differentiate into short-lived plasma cells. The plasma cells release antibody molecules. (b) (i) Outline how plasma cells produce antibody molecules. … … … … … … … … … … … … [4] (ii) Describe how antibody molecules are released from the plasma cell. … … … … [2] (c) The cells labelled R on Fig. 4.1 divide to give more cells that do not differentiate into plasma cells. These cells have an important role in the immune system. Explain the role of these cells. … … … … … … [3]

9 9700/21/M/J/14 © UCLES 2014 [Turn over The mass of DNA in the cells shown in Fig. 4.1 was determined. The results are shown in Fig. 4.2. mass of DNA in each cell / picograms time W Z 0 1 2 3 4 5 6 7 Fig. 4.2 (d) State what happens at W and Z to change the mass of DNA in each cell. W … Z … [2] (e) Acute lymphoblastic leukaemia (ALL) is a cancer of B-lymphocytes. It is very rare in adults, but more common in children. A study in 2009 found that exposure to tobacco smoke in the home may put children at risk of developing ALL. Suggest how smoking by adults in the home may put their children at risk of cancers, such as ALL. … … … … … … … … [3] [Total: 18]

10 9700/21/M/J/14 © UCLES 2014 5 Fig. 5.1 shows a vertical section of the left side of the heart of a mammal. valve tendon papillary muscle atrioventricular valve Fig. 5.1 (a) Explain the difference in the thickness of the left ventricle and the left atrium. … … … … …[2]

11 9700/21/M/J/14 © UCLES 2014 (b) Explain how the structures labelled on Fig. 5.1 ensure that blood flows in the correct direction. … … … … … … …[3] (c) During one cardiac cycle, blood is pumped from the heart into the pulmonary and systemic circulations. Explain how the contraction of the four chambers of the heart are coordinated and controlled to enable blood to be pumped simultaneously into both the pulmonary and systemic circulations. … … … … … … … … … … … …[4] [Total: 9]

12 9700/21/M/J/14 © UCLES 2014 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. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. BLANK PAGE

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2014 series 9700 BIOLOGY 9700/21 Paper 2 (AS Structured Questions), maximum raw mark 60 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2014 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

Page 2 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 Mark scheme abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question, or by extra guidance) AW alternative wording (where responses vary more than usual) underline actual word given must be used by candidate (grammatical variants accepted) max indicates the maximum number of marks that can be given ora or reverse argument mp marking point (with relevant number) ecf error carried forward I ignore

Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 1 (a) award two marks if correct answer within range 29 000 to 31 000 is given allow ± 3 mm in reading the line, e.g. 3.0 000 90 6 3 10 3.0 10 90 − × × 9 2 10 3.0 10 9.0 − − × × (×) 30 000 / 3 × 104 ;; one mark if not rounded to nearest whole number one mark if a unit (mm, µm) is given one mark if line is measured and given in mm or cm within accepted range and divided by 3.0 µm but incorrect conversion factor used for the line measurement or 3.0 µm [2] (b) feature identity name provides motility F flagellum stores genetic information G DNA ; I any description, e.g. loop of / circular A chromosome(s) / nucleoid R plasmid / chromatid partially permeable C cell surface / plasma, membrane ; A phospholipid bilayer composed of murein (peptidoglycan) E cell wall ; R cellulose cell wall site of translation A (70S / 18 nm) ribosome(s) ; R 80S / 22 nm / larger, ribosome [4]

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 (c) A (double) membrane-bound organelles only if no examples given (true) nucleus / nuclear envelope ; A nuclear membrane I well-defined chloroplast ; A grana / thylakoid(s) A plastid (permanent) vacuole / tonoplast ; R vesicles unqualified A lysosome mitochondrion / mitochondria ; A cristae Golgi (body / apparatus / complex) / dictyosome ; A Golgi vesicle(s) rough endoplasmic reticulum / rough (ER) / RER ; smooth endoplasmic reticulum / smooth ER / SER ; A endoplasmic reticulum, if RER and SER not given nucleolus ; linear / AW, chromosomes ; A DNA + histones cellulose cell wall ; starch grain / amyloplast ; plasmodesma(ta) ; larger / 80S / 22 nm, ribosomes ; [max 3] (d) one mark for infected person with contaminated faeces, e.g. faeces / sewage, contaminates (drinking) water / cooking utensils / vegetable plots / crops / food ; A diarrhoea for faeces R (human) waste unqualified A ref. to houseflies landing on contaminated faeces one mark for uninfected person eating contaminated food / using contaminated utensils / drinking contaminated water ; A bacteria enters water in context of drinking R infected food or water I handling contaminated food A faecal-oral route for two marks [2] (e) pathogen is at most vulnerable when in transfer between hosts / AW ; A idea of breaking the transmission cycle 2 max for the following control methods: sewage treatment / (effective) sanitation / correct ref. to positioning of latrines ; do not use human faeces for fertiliser ; piped / treated / boiled / chlorinated / purified, (drinking) water ; A sanitised / clean, water I cooking refs. A water treatment with UV / ozone bottled water ; water treatment plants upstream of sewage disposal ; (to reduce pool of infected people) antibiotics or oral / intravenous, rehydration (therapy) ; A ORT [max 3] [Total: 14]

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 2 (a) population ; community ; (photo)autotroph / (primary) producer ; (ecological) niche ; [4] (b) provides ammonium (ions) / ammonia / nitrogen(ous) compounds / fixed nitrogen / organic nitrogen ; A organic compounds R nitrate / nitrite R nitrate / nitrite, and ammonia A formulae NH3 / NH4 + if only a formula is used then it must be completely correct accept the following in context of plants / animals for synthesis of amino acids / nucleotides ; synthesis of protein / nucleic acids / DNA / RNA ; proteins required for, growth / enzymes / tissue repair / AW ; nucleic acids for storage of genetic information / AW ; idea of offsets loss of, (fixed) nitrogen / nitrate ions ; reduces effect of (fixed) nitrogen as a limiting factor (for growth) ; [max 3] [Total: 7] 3 (a) (i) –H and –OH indicated ; A –OH on end of amylose and –H on alpha glucose water eliminated / condensation ; A dehydration oxygen bridge / glycosidic bond, drawn between C1 and C4 ; If the whole glucose molecule and / or the end of the amylose molecule has not been drawn, then only award mp3 if C1 and C4 are indicated in some way, e.g. by numbering them or putting in the hydrogens. [3] (ii) (1,4 / 1,6) glycosidic ; A glucosidic A phonetic spelling of glycosidic [1]

Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 (b) feature amylose glycogen cellulose type of glucose α-glucose α-glucose β-glucose ; branched or unbranched molecule unbranched branched unbranched / not branched ; role in organisms energy storage energy storage structural / (component of) cell walls / tensile strength / dietary fibre / roughage ; I support [3] (c) (i) maltase and maltose must be correctly referenced ignore references to reversible/irreversible (ascorbase) binds to / fits into / enters active site ; complementary (shape) to active site ; so substrate / maltose, cannot enter / cannot bind ; A no / few, ES complex A prevents formation of ES complexes A ascorbase forms enzyme inhibitor complex competes with substrate / competitive inhibition ; slows the (rate of), digestion / hydrolysis / breakdown, of maltose ; R ‘stops the reaction’ R if in context of starch alternative answer if candidates assume ascorbase is an enzyme: ascorbase, breaks down / digests / hydrolyses, maltase ; A ascorbase destroys the active site of maltase so no enzymes to digests maltose ; slows / stops, reaction / digestion / hydrolysis / breakdown, of maltose ; [max 3] (ii) inhibits / slows down / prevents, breakdown / (catalysing) hydrolysis / digestion, of maltose (to glucose) ; I starch less glucose is absorbed / passes across membranes / enters blood ; [2] [Total: 12]

Page 7 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 4 (a) (i) non-self foreign / AW ; A ref. to epitope(s) I pathogen / organism antigen macromolecule / (glyco)protein / carbohydrate / polysaccharide / oligosaccharide ; stimulates / AW, an immune response / production of antibodies ; A results in formation of antigen-antibody complexes A other described events in an immune response [max 2] (ii) antibody / immunoglobulin / IgG, on cell surface / on cell membrane ; (act as) receptors ; ref. to antigen-binding / AW ; (shape) specific / complementary, to antigen ; [max 2] (b) (i) DNA / gene transcribed / mRNA using DNA as template / AW ; A transcription unqualified idea of mRNA associating with ribosome(s) ; ref. to tRNA with specific amino acid (carried to ribosome) ; pairing / AW of codons on mRNA with anticodons on tRNA ; formation of peptide bonds (between adjacent amino acids) ; antibody / protein / polypeptide(s), enters RER / moves to Golgi body ; ref. to forming, secondary / tertiary structure ; antibody / protein / polypeptide(s), modified / processed / glycosylated / formation of quaternary structure / formation of disulphide bond(s) in Golgi (body / apparatus / complex) ; I ref. to packaging [max 4] (ii) vesicles move to cell / surface / plasma, membrane (via cytoskeleton) ; R secreting vesicles unqualified vesicles fuse with cell (surface) membrane / exocytosis ; R active transport movement of vesicle / exocytosis requires energy or ATP / is active ; [max 2] (c) memory cells ; A form immunological memory I ‘gives immunity’ remain / stay in circulation / blood / lymphatic system ; R ‘last a long time / long lived’ unqualified for secondary response ; fast(er) response when exposed again to same pathogen / same antigen ; A fast(er) clonal selection / fast(er) clonal expansion A divide quickly / rapidly A long(er) lasting response to form plasma cells (and more memory cells) ; more antibodies produced / higher concentration of antibodies ; R if in context of memory cells to prevent person feeling ill / to prevent symptoms ; [max 3]

Page 8 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 (d) W – cytokinesis / cytoplasmic division / cell divides into two ; I cell division R mitosis / telophase Z – (semi-conservative) replication (of DNA) ; I S phase / interphase of cell cycle R copying of DNA R protein synthesis R if replication is given in any other phase of the cell cycle [2] (e) 1 breathing in / inhale smoke / ‘second hand’ smoke / sidestream smoke ; A passive smoking I exposed to smoke 2 (tobacco smoke contains) carcinogen(s) ; 3 causes mutation / described ; e.g. change to / alters / damages, DNA R if in wrong type of cell 4 leads to uncontrolled cell division / mitosis / growth ; 5 forming a tumour / mass of cells ; 6 correct ref. to (proto-)oncogenes / tumour suppressor genes ; e.g. formation of oncogenes / mutation of tumour suppressor genes / ‘switching off’ tumour suppressing genes mutation of correct named gene = 2 marks e.g. mutation of tumour suppressor gene P53 (gene) mutates = 2 marks [max 3] [Total: 18] 5 (a) more / thicker, (cardiac) muscle (tissue) in left ventricle ; A ora A thicker muscular wall either atrium pumps blood at lower pressure / against less resistance / to ventricle / short(er) distance / with less force ; or ventricle pumps blood to the body / into systemic circulation / long(er) distance / against greater resistance / at higher pressure / with more force ; R ventricle wall withstands high pressure [max 2]

Page 9 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 21 © Cambridge International Examinations 2014 (b) valve opens to allow blood flow from atrium into ventricle / when pressure in atrium is greater than pressure in ventricle / during atrial systole ; valve closes when ventricle contracts / when pressure in ventricle is greater than pressure in atrium / during ventricle systole ; during contraction of ventricles papillary muscles contract to ‘pull on’ tendons ; R if tendons are said to open the valve tendons prevent valve, inverting / going inside out / everting / AW ; [max 3] (c) 1 sino-atrial node / SAN sends out, waves of excitation / waves of depolarisation / (electrical) impulses / action potential(s) ; R nervous impulses / signal / message penalise once only 2 wave of excitation / AW / SAN stimulates, (both) atria to contract / atrial systole ; 3 fibrous ring / non-conducting tissue / insulating tissue (between atria and ventricles), prevents impulse reaching the ventricles / prevents atria and ventricles contracting at the same time ; 4 atrio-ventricular node / AVN delays impulse (by 0.1 s) / prevents ventricles contracting at the same time as atria ; 5 allows, atria to empty / ventricles to fill ; 6 AVN sends out, waves of excitation / impulses to Purkyne tissue / Bundle of His (in septum) ; 7 causes ventricles to contract together / at the same time / simultaneously / AW ; [max 4] [Total: 9]