The structures of the amino acids serine and lysine are shown in Fig. 9.1. [Figure 9.1]

1. (a)Draw the structure for the dipeptide, ser-lys, with molecular formula C9H19N3O4. The peptide functional group formed should be displayed.[2]
2. (b)(i)The isoelectric point of serine is 5.7 and of lysine is 9.7. State what is meant by isoelectric point.[1]
3. (b)(ii)A mixture of serine, lysine and ser-lys is analysed by electrophoresis using a buffer at pH 5.7. [Figure 9.2] Draw and label three spots on Fig. 9.2 to indicate the predicted position of each of these three species, serine, lysine and ser-lys, after electrophoresis. Explain your answer.[3]
4. (c)(i)Fig. 9.3 shows the synthesis of compound R from compound P. [Figure 9.3] Draw the structure of Q in Fig. 9.3.[1]
5. (c)(ii)State the reagents and conditions for steps 1 and 2 in Fig. 9.3. step 1 ............................................ step 2 ............................................[2]

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