Cambridge A Level Biology 9700 — 2002 May/June Paper 4 · Variant 1

This question paper consists of 11 printed pages and 1 blank page. SP (CW/JG) S24435/3 © CIE 2002 [Turn over CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level BIOLOGY 9700/4 PAPER 4 Structured Questions A2 Core MAY/JUNE SESSION 2002 1 hour Candidates answer on the question paper. No additional materials are required. TIME 1 hour INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page. Answer all questions. Write your answers in the spaces provided on the question paper. All working for numerical answers must be shown. INFORMATION FOR CANDIDATES The intended number of marks is given in brackets [ ] at the end of each question or part question. Candidate Centre Number Number Candidate Name FOR EXAMINER’S USE 1 2 3 4 5 TOTAL

2 9700/4/M/J/02 Answer all the questions. Write your answers in the spaces provided. 1 Fig. 1.1 shows the flow of electrons in non-cyclic and cyclic photophosphorylation. Fig. 1.1 (a) State the precise location of photophosphorylation in a chloroplast. …[2] (b) Describe the role of light in photophosphorylation. … … …[2] For Examiner’s Use PSII PSI PSI - photosystem I PSII - photosystem II etc - electron transport chain e- - electron e- etc e- light energy light energy high low electron energy level PSI etc light energy high low key non-cyclic photophosphorylation cyclic photophosphorylation

3 9700/4/M/J/02 [Turn over (c) Explain how non-cyclic photophosphorylation differs from cyclic photophosphorylation. … … … … … …[4] (d) Paraquat is a herbicide that prevents the flow of electrons from photosystem I and reduces oxygen to a chemically reactive superoxide radical. This results in severe damage to chloroplasts. It is now possible to make a crop plant resistant to such herbicides. Suggest a use for such plants. … …[1] [Total : 9] For Examiner’s Use

4 9700/4/M/J/02 2 (a) Define the term respiratory quotient (RQ). … …[1] (b) Explain the significance of the different values that may be obtained of RQ. … … …[2] Two respirometers were set up as shown in Fig. 2.1. Fig. 2.1 closed three-way tap soda lime cotton wool germinating seeds boiled seeds 5cm3 syringe reservoir manometer tube water-bath For Examiner’s Use

5 9700/4/M/J/02 [Turn over (c) Outline how this apparatus is used to measure the rate of oxygen uptake by a known mass of germinating seeds. … … … … … …[4] (d) Explain how the apparatus could be modified to measure the RQ of the germinating seeds. … … …[2] (e) Explain why an increase in temperature from 15 °C to 25 °C will increase the rate of oxygen uptake in germinating seeds. … … …[2] [Total : 11] For Examiner’s Use

6 9700/4/M/J/02 3 Fig. 3.1 shows part of an axon with its associated Schwann cells. Fig. 3.1 (a) Explain how charged ions, such as Na+ and K+, are able to pass across membranes of nerve cells. … … …[2] (b) Describe the role in impulse transmission along a nerve cell of (i) Na+; … … …[2] (ii) K+. … … …[2] node of Ranvier axon membrane myelin laminations of Schwann cell axon For Examiner’s Use

7 9700/4/M/J/02 [Turn over (c) Describe the function of the myelin sheath. … … … … …[3] (d) Suggest how the intensity of a stimulus can be passed along a single nerve cell. … …[1] [Total : 10] For Examiner’s Use

8 9700/4/M/J/02 4 Fig. 4.1 shows a kidney tubule, collecting duct and associated blood vessels. Fig. 4.1 (a) Describe the function of the (i) glomerulus; … … …[2] (ii) peritubular capillaries; … … …[2] medulla cortex glomerulus peritubular capillary artery vein collecting duct vasa recta For Examiner’s Use

9 9700/4/M/J/02 [Turn over (iii) vasa recta. … … …[2] (b) Explain the role of the collecting duct in controlling the water content of body fluids. … … … …[3] (c) Suggest two disadvantages of the use of dialysis machines in treating kidney failure. … … …[2] [Total : 11] For Examiner’s Use

10 9700/4/M/J/02 5 Pure-breeding pea plants with round, yellow seeds were crossed with pure-breeding pea plants with wrinkled, green seeds. The offspring all had round, yellow seeds. These seeds were grown and the resultant plants allowed to self-pollinate. This produced 1112 offspring with the following characteristics. 630 round, yellow seeds 202 round, green seeds 216 wrinkled, yellow seeds 64 wrinkled, green seeds (a) Using the symbols R for round, r for wrinkled, B for yellow and b for green, draw a genetic diagram to explain these results. [4] For Examiner’s Use

11 9700/4/M/J/02 (b) Explain why the wrinkled, green seeds produced pure-breeding offspring, while the round, yellow seeds did not. … … … …[3] (c) A ratio of 9:3:3:1 was expected. A chi-squared test was carried out to test the significance of the differences between the observed and expected results. This gave a value of 0.47. With reference to the table of probabilities, explain how the value for the chi-squared test supports the hypothesis that these are two pairs of segregating alleles at two loci. … … … …[2] [Total : 9] For Examiner’s Use probability 0.99 0.98 0.95 0.90 0.50 0.10 0.05 0.02 0.01 at 3 degrees 0.12 0.19 0.35 0.58 2.4 6.3 7.8 9.8 11.3 of freedom

CAMBRIDGE INTERNATIONAL EXAMINATIONS JUNE 2002 GCE Advanced Level MARK SCHEME MAXIMUM MARK : 50 SYLLABUS/COMPONENT :9700 /4 BIOLOGY (STRUCTURED QUESTIONS (A2 CORE)) PRY UNIVERSITY of CAMBRIDGE “9 Local Examinations Syndicate

f Page 1 Mark Scheme | Sylfabus [ Paper A Level Examinations — June 2002 [9700 “| 4 Question 1 {a) thylakoid (membrane) / lamellae ; in graha ; : . 2 (b) source of energy ; to excite electrons ; for synthesis of ATP (from ADP) ; and reduced NADP / NADPH / NADPH; / NADPH ; ref. photolysis (of water) ; 2max (c} 1 electron lost from photosystem 1! / non cyclic has PSII and PS! / cyclic has only PS! ; 2 replaced by electron from water in noncyclic ; 3 ref. to photolysis of water / oxygen produced in noncyclic ; 4 non cyclic produces reduced NADP / NADPH / NADPH: / NADPH’ : 5 excited eleciron retums to chlorophyll / photosystem 1 in cyclic ; 6 electron not taken from. hydroxy ion / water. in cyclic; , Amax (a) idea that paraquat can be used to kill weeds around growing crop ; 1 Totai: 9 Question 2 (a) tatio of volume / moles / amount of carbon dioxide evolved to volume of oxygen absorbed in respiration ; 1 {b) depends on substrate ; greater than 1 some anaerobic respiration / ref. to a anaerobic respiration ; carbohydrate 1 / protein 0.9 / fat 0.7 ;; 2 outof 3 ref. to other metabolic processes using oxygen / produce carbon dioxide ; 2 max () time / allowed to equilibrate ; record levet of fluid in manometer ; change in known time / ref. time ; repeat ; open clip and reset level ; ref units ; ref to boiled seeds as a controt ; as soda lime absorbs carbon dioxide given off ; ref. to calculation ; 4max (a) remove soda lime ; repeat experiment / ref. to comparison ; fef. to whether manometer rose or fell ; ref. to catculation ; 2max (e) ref effect of temperature on enzymes in respiration ; ref. named effect of temperature eg increased collisions / kinetic energy / more substrate molecules with activation energy ; ref. to Qi =2 2max Total : 14

Page 2 L.- Mark Scheme Syllabus | Paper I A Level Examinations — June 2002 9700 4 | Question 3 {ay channe! proteins ref. gated ; Na’ K’ / cation pump / carier protein ; diffusion down electrochemical gradient ; 2max tb) 0) Na’ in; cause depolarization / figures -GOmV to +40mV ; fet, action potentiat ; 2 max @) = K out; restores resting potential / repolarisation : 2 {c) acts as an insulator ; action potential cannot fire in part of axon covered by myelin sheath / onty at node of Ranvier ; Na*./ K* camot pass across jumps from node to node / ref. saltation / ref. to local circults; speeds up impulse transmission ; . 3 max fequency of impulses ; 1 Total : 10 Question 4 {a} (i) formation of glomerular filtrate / ultrafiltration / pressure filtration ; (soluble) molecules / water, urea, glucose in ptasma forced into nephron / kidney tubule ; 2 (ii) removing reabsorbed molecules ; water / ghicose ; 2 {iil}, |= removing water ; from / reabsorbed by collecting ducts ; ref. to maintain water potential gradient (in medulla) 2max {b) permeability can be varied ; correct ref. to ADH ; if (blood) water level / potential is low more water reabsorbed ; if (blood) water level / potential too high litte / no water reabsorbed ; 3 max {c) diet has to be regulated carefully when not on the machine ; tisk of infection ; Simited mobility when on machine / ref. to time on machine ; ref, to expense ; difficulty of finding veins / damage to veins ; AVP; 2max Total : 11 i

| Page 3 I Mark Schame Syllabus | Paper | | A Level Examinations — June 2002 9700 4] Question 5 fa) correct parental genotype ; correct gametes ; correct genotypes of offspring ; correct phenotypes of offspring linked fo genotypes; 4 RrBb x RrBb RB Rb rB rb | RB RbrB rb RB Rb 8 | RrBb | Rrbb | Bb rrbb Round yellow Round green Wrinkled yellow Wrinkied green RRBB RRBb RRbb BB ebb RrBB RrBb Rrbb rrBb {b) wrinkled seeds homozygous / double recessive ; round yellow seeds variety of different genotypes / may be heterozygotes ; round yellow seeds some do breed true / homozygous dominant; 3 {c) probability of as large a deviation as 0.47 is between 0.9 and 0.95 ; indicating a close fit to the expected resutts / they do not differ statistically from the expected resutt ; 2 Total : 9