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CIE Jun 2015 v3 Paper 4 Q8
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![14 Section B Answer all the questions in the spaces provided. Proteins are formed by the polymerisation of amino acids. (a) (i) State the type of chemical reaction used to form these polymer chains.[1] (ii) The amino acids serine and valine can combine together to form a dipeptide. OH OH H2N serine, ser H2N OH valine, val Draw the skeletal structure of the dipeptide val-ser. [2] (iii) Suggest how the type of amino acids in a protein determines its three-dimensional structure.[2]UCLES 2015 9701/43/M/J/15<br />
(b) Using labelled diagrams or words as appropriate, explain 15 (i) why a particular enzyme may only catalyse a speci c reaction on a speci c substrate,[2] (ii) how non-competitive inhibition of an enzyme-catalysed reaction can occur.[3] [Total: 10]UCLES 2015 9701/43/M/J/15 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/June_2015_v3_QP_-_Paper_4_CIE_Chemistry_A-level_8-0.jpg)
![Page 6 Cambridge International A LevelMay/June 2015 Mark Scheme Syllabus Paper 9701 43 (a) (i) heat with catalyst or heat with Al2O3 / SiO2 (ii) B is CH3CH2CH3 (iii) C is CH2=CHCH2CH2CH3 D and E are CH3CH=CHCH2CH3 (one shown as cis, the other as trans) F is CH3CH2CH2CO2H G is CH3CO2H H is CH3CH2CO2H (iv) geometrical or cis-trans or EZ (b) (i) No particular conditions or in the dark (ii) electrophilic addition (iii) CH3 CH CH2 + Br - Br CH3 CH3 CH CH2 CH CH2 Br Br Br Br 1 1 1 1 1 (a) (i) condensation (ii) (iii) any two side-chain interactions mentioned with group Ionic attractions / bonds between CO2and NH3 van der Waals between alkyl / aryl / non-polar groups or valine hydrogen(H) bonding between OH, NH2, COOH, NH or serine SS or disulfide bonds or disulfur bond / bridge between SH groups or cysteineCambridge International Examinations 2015 [Total: 10]<br />
Page 7 Cambridge International A LevelMay/June 2015 Mark Scheme Syllabus Paper 9701 43 (b) (i) labelled diagrams or in wordsthe enzyme has a specific shape or substrate shape is complementary to active site the substrate bonds / binds / fits to the active site or other substrates do not fit into active site (ii) labelled diagrams or in words inhibitor binds to enzyme away from the active site or inhibitor binds to allosteric site this changes the shape (or structure) of the active sitesubstrate no longer fits the active site 1 1 1 1 1 [Total: 10] 1 1 (a) (i) use restriction enzymes or using an enzyme to break (the DNA) down into smaller fragments (ii) use the polymerase chain reaction or use DNA polymerase to replicate / copy (the sample of DNA) amino acids have different charges due to their side-chain / R group / pH / CO2 and NH3 (iii)+ groupsDNA fragments have negatively-charge phosphates(or PO4) or DNA has PO4 groupsCambridge International Examinations 2015<br />](https://learnah.org/wp-content/uploads/2018/08/June_2015_v3_MS_-_Paper_4_CIE_Chemistry_A-level_8-0.jpg)
