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ANS P2 - CAMBRIDGE INTERNATIONAL EXAMINATIONS JUNE 2002 GCE...

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Unformatted text preview: CAMBRIDGE INTERNATIONAL EXAMINATIONS JUNE 2002 GCE Advanced Subsidiary Level MARK SCHEME MAXIMUM MARK : 60 SYLLABUSICOMPONENT :9700 12 BIOLOGY (STRUCTURED QUESTIONS (AS)) UNIVERSITY af CAMBRIDGE Local Examinations Syndicate 22%“ Page 1 Mark Schema Syllabus Paper AS Level Examinations —- June 2002 9700 2 Question Expected Answers Marks 1 (a) M between zygote and young seaweed f between young seaweed and adult; I (h) each chromosome contains two chromatids; (genetically) identical ! exact replica; daughter cells receive a copy of, each chromosome 2’ DNA molecule 4" same genetic material I AW; 2 max (c) each strand ;’ polynucleotides, acts as a template f sense strand; for complementary, strand f polynucleotides! nucleotides 3' base pairing; new DNA contains half old, half new; 2 max ({1} reduction division; gametes ! sex cells I eggs and sperms, have half the chromosome number ! haploid r’ n; zygote is diploid f has full number of chromosomes 2’ 2n; chromosome number remains the same i does not increase with each generation; 3 mar. {Total : 8] Page 2 Mark Scheme Syllabus Paper _ AS Level Examinations - June 2002 9700 2 Question Expected Answers Marks 2 (a) all hydrogen pet-etude broken down I no Substrate left I substrate limiting; l (b) Line below that at 20°C may reach same plateau or heading towards it; 1 (c) no reaction I very little oxygen :’ gas collected :’ no oxygen} gas collected; (1' mark) man: 2 for expionotiort catalasef enzyme, denatured; loss of tertiary structure I conformation a“ folding! shape I“ active site changes; breakage of bonds; named bonds (hydrogen, ionic); substrate no longer fits active site I no enzyme substrate complex formed; 3 max (:1) repeat using different concentrations of hydrogen peroxide a” substrate; ref to (suitable) range} details of concentrations; fresh solution of catalase f enzyme each time; same concentration of catalase f enzyme; same temperature 1‘ same pH; repeat readingsf replicates; calculate initial rate; method {e.g. voltune in 15 seconds f gradient); 4 max [Total : 9] Page 3 | Question 3 (a) (b) (i) (ii) (iii) Mark Scheme Syllabus Paper | AS Level Examinations —June 2002 9700 2 l Expected Answers Marks phospholipid; J 1 glycerol; 2 fatty acid{s) f hydrocarbonfi) (tails f chains); phosphate; 3 phogpholipids are, fluid 1 liquid I move about ;’ diffuse within own monolayer; proteins (are separate pieces) ‘floating’ f moving about in liquid 1’ AW; ref to pattern I arrangement of proteins; 2 max variable region I AW; . difi'erent I particular, sequences of amino acids J primary structure; different, (3 D) shapes f conformation f folding f tertiary' structure; ref to R groups“:F side chains; complementary to 3' matches shape of antigen(s); 3 max [Total : 9] Question 4 {a} (b) (d) l Mark Scheme Syllabus Paper | AS Level Examinations — June 2002 97061 2 Expected Answers Marks ventricle contracts i" ventricular systole; blood forced through semi-lunar valve; into aorta; attic-ventricular 1‘ bicuspid I mitral valve closed; 2 max ref to unidirectional valves} valves prevent backflow; blood pressure greater on one side of valve than the other: atrial systole! contraction forces open atrio-ventricuiarf bicuspid f mitral valve; ventricular Systole I contraction closes atrio-ventricular ! bicuspid f mitral valve; semi-lunar valve opens (in context of ventricular systole); semi-lunar valve closes (after ventricular systole); ref to role of tendons: ref to role ofpapiliary muscles; 3 max (pressure falls to zero because} all blood expelled from ventricle r' ventricle completely empties f AW; (blood pressure falls to lePa} because elastic fibres qualified f elasticity of arteries f elastic recoil; ref to smooth muscles qualified; narrow diameter of capillaries f arterioles r' m arteries; resistance to flow; 3 ma: nicotine causes constriction of blood vessels; nicotine raises, blood pressure!r heart rate; nicotine causes blood platelets to become ‘sticky‘ forming blockage {Tbfi nicotine :’ carbon monoxide, damages artery lint—'ng ! endothelium; increased risk of atherosclerosis f thrombus; atherosclerosis described (eg. ref to deposition of fatty material a“ atheromaf fatty plaque f cholesterol); carbon monoxide reduces oxygen transport f levels; 3 max [Total : ll} Page 5 Mark Scheme | Syllabus as Level Examinations — June 2002 I, 9700 ‘- Question Expected Answers _Marks 5 (a) decrease in response to drug I effects of drug become less intense; more drug taken to achieve same efiect; increased rate of metabolism of drug; decrease in sensitivity of receptors f more receptors made; body cannot fimction without drug a“ drug becomes part of metabolism; ref ndthdrawal symptoms f abstinence syndrome; 3 max (b) fatty liver 1" fat accumulates; hepatitis, inflammation (of liver); cells die; fibrous tissue a“ collagen (accumulates); nodules, described (tag. hard it no blood Supply 1‘ disrupt arrangement of cells); cirrhosis; liver cancer; 4 ma: [Total : 7] Question Expected Answers Marks 6 (a) (i) A nitrogen fixation; B nitrification; C denitrification; 3 (ii) legumes ! green manure f compost I organic matter I humus f manure f AW ploughed into soil; decay .-" decomposition to release ammoniumlF (ions) annnonification 1 form nitrates; grow legumes for nitrogen fixation; crop rotation f intercropping i' alley cropping; improve aeration;If drainage (in context of favouring nitrification f reducing denitrification; 3 max [Total : 6] Total mark for paper = 50 ...
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