Version 1.0 12/07 Version 1.0 12/07 c General Certificate of Education Biology 5416 Specification B BYB1 Core Principles Mark Scheme 2008 examination - January series Mark schemes are prepared by the Principal Examiner and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation meeting attended by all examiners and is the scheme which was used by them in this examination. The standardisation meeting ensures that the mark scheme covers the candidates’ responses to questions and that every examiner understands and applies it in the same correct way. As preparation for the standardisation meeting each examiner analyses a number of candidates’ scripts: alternative answers not already covered by the mark scheme are discussed at the meeting and legislated for. If, after this meeting, examiners encounter unusual answers which have not been discussed at the meeting they are required to refer these to the Principal Examiner. Mark schemes are prepared by the Principal Examiner and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation meeting attended by all examiners and is the scheme which was used by them in this examination. The standardisation meeting ensures that the mark scheme covers the candidates’ responses to questions and that every examiner understands and applies it in the same correct way. As preparation for the standardisation meeting each examiner analyses a number of candidates’ scripts: alternative answers not already covered by the mark scheme are discussed at the meeting and legislated for. If, after this meeting, examiners encounter unusual answers which have not been discussed at the meeting they are required to refer these to the Principal Examiner. Further copies of this Mark Scheme are available to download from the AQA Website: www.aqa.org.uk Copyright © 2008 AQA and its licensors. All rights reserved. COPYRIGHT AQA retains the copyright on all its publications. However, registered centres for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to centres to photocopy any material that is acknowledged to a third party even for internal use within the centre. Set and published by the Assessment and Qualifications Alliance. The Assessment and Qualifications Alliance (AQA) is a company limited by guarantee registered in England and Wales (company number 3644723) and a registered charity (registered charity number 1073334). Registered address: AQA, Devas Street, Manchester M15 6EX Dr Michael Cresswell Director General BYB1 - AQA GCE Mark Scheme 2008 Jan series BYB1 - AQA GCE Mark Scheme 2008 Jan series (a) Cell Feature Nucleus Cell wall Cell surface membrane Ribosomes Epithelial cell from the small intestine v X v v Palisade mesophyll cell v v v v Bacterium X v v v 3 (b) Helical/spiral/coiled (shape) – compact; Insoluble – osmotically inactive / does not leave cell; Large size– does not leave cell / many glucose/monomers; Branched – glucose/monomers easily/quickly removed; 2 max (Two features without explanations = one mark) (c) Provides glucose for respiration/as energy source/for ATP production; 1 Total 6 Question 2 (a) Biuret / copper sulphate and sodium hydroxide; 1 (b) (i) 39.8 - 39.9g; 1 (Allow 39.6) (ii) No double bonds between carbons/in hydrocarbon chain; 1 (Allow appropriate description) (c) (i) Heat with benedict’s (solution); Red / orange colour; 2 (ii) Standardised technique e.g. same amount of biscuit / same volume of benedict’s / heat for same period of time; Compare colour / compare mass (of precipitate) / rate of colour production / different colours / use a colorimeter; 2 Total 7 3 BYB1 - AQA GCE Mark Scheme 2008 Jan series BYB1 - AQA GCE Mark Scheme 2008 Jan series (a) Principle of dividing measured length by 10400; (Ignore units) 8.6 - 8.75; 2 (Correct answer gains two marks) (b) Rough endoplasmic reticulum produces/transport protein/involved in translation; Ribosomes produces/transport protein/involved in translation; Golgi body modifies proteins/enzymes / produce glycoproteins/vesicles; Mitochondria provide ATP/energy; Nucleus has DNA/genetic code for protein synthesis/transcription; Vesicle / lysosome fuses with membrane/for exocytosis; 2 max (c) (i) Mass /density; 1 (ii) Prevents osmosis / no (net) movement of water (into / out of organelle); So (organelle) does not burst / shrivel; 2 (Damage = neutral) (Reference to cell rather than organelle negates first mark obtained) Total 7 Question 4 (a) (i) Condensation; 1 (ii) Dipeptide and water; 1 (Any order) (b) Protein receptors / glycoproteins; Specific tertiary/3D structure / complementary (shape); 2 (Reference to active site negates second marking point) (c) (i) Principle of dividing by 85 - 86/8.5 - 8.6; 0.19 - 0.27; 2 (No marks for correct answer derived incorrectly) (ii) More soluble; 1 (iii) Asp and glu; 1 Total 8 4 BYB1 - AQA GCE Mark Scheme 2008 Jan series BYB1 - AQA GCE Mark Scheme 2008 Jan series (a) (i) Villus; 1 (ii) Long length / folds / microvilli; 1 (b) (i) Diffusion / facilitated diffusion; 1 (ii) Active transport; Requires energy; Carrier proteins; OR Move in with sodium (ions); Carrier/channel proteins / symporters; Active transport (of ions); 3 (iii) More carriers / different rate of action of carriers; 1 Total 7 Question 6 (a) Large surface area to volume (ratio); Short diffusion distance; 2 (b) Water and blood flow in opposite directions; (Oxygen) concentration gradient/difference maintained; Maintains diffusion (gradient) / diffusion always occurs; 3 (c) Increase in temperature increases rate of ventilation; (More) oxygen required for (increase in) respiration / less dissolved oxygen at higher temperatures; 2 Total 7 5 BYB1 - AQA GCE Mark Scheme 2008 Jan series BYB1 - AQA GCE Mark Scheme 2008 Jan series (a) Formation of melanin (increases colour intensity); 1 (b) (i) Steeper increase, reaching same colour intensity; 1 (ii) Less steep increase, which would reach same colour intensity; 1 (c) Competitive inhibitor (not a mark) 1 2 3 Inhibitor similar in shape to substrate; (Reject ‘same’) Competes for active site / binds at active site; (Reject ‘reacts with’) Less substrate attaches / fewer enzyme-substrate complexes; Non-competitive inhibitor (not a mark) 4 5 6 Inhibitor differs in shape to substrate; Binds at position other than active site/ binds at allosteric site/inhibitor site; Alters active site so substrate cannot bind / substrate attaches but no reaction/product; 6 (d) Addition of extra substrate; Rate of reaction increased if competitive / no change if non-competitive; 2 Total 11 6