CIE Jun 2014 v2 Paper 4 Q7

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16 Modern methods of chemical analysis often rely on the interpretation of data gathered from instrumental techniques. (a) Electrophoresis and paper chromatography can both be used to separate amino acids from a mixture obtained from polypeptides. PMT d.c. power supply glass slides lid paper amino acid mixture placed here filter paper soaked in buffer solution solvent front mixtures placed here solvent electrophoresis paper chromatography In each case, give one property of the amino acids that causes their separation. electrophoresispaper chromatography[2] (b) Amino acids are colourless. How are the positions of the different amino acids made visible so that measurements can be made?[1] (c) Which measurements need to be made in order to identify individual amino acids in paper chromatography?[1]UCLES 2014 9701/42/M/J/14<br /> (d) The diagram shows the results of electrophoresis on a mixture of the amino acids glycine, lysine and glutamic acid at pH 7.0. The structures of the amino acids at pH 7.0 are shown. 17 PMT glycine: lysine: glutamic acid: H3N+CH(CH2CH2CO2 H3N+CH2CO2 H3N+CH(CH2CH2CH2CH2NH3+)CO2 )CO2 spot of mixture applied here Identify the amino acids responsible for the spots labelled R, S and T. RST[3] (e) This diagram shows the results of two-way paper chromatography of a mixture of amino acids. solvent 1 mixture applied here solvent 2 To answer these questions you need to indicate clearly on the diagram above as directed in the questions. (i) Put a U next to the amino acid that travelled furthest in solvent 2. (ii) Put a ring around the two amino acids that were not separated in solvent 1. (iii) Put a W next to the amino acid that was very soluble in both solvents.UCLES 2014 9701/42/M/J/14 [3] [Total: 10] [Turn over<br />

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