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a) A naturally occurring amino acid, 1a, has the following structure: OH i) What is the molecular formula of 1a? [1 mark] What three functional groups does 1a contain? [3 marks) ii) ii) Draw tetrahedral representations of both R and 5 enantiomers of 1a (4 marks] b) The effect of pH on the form of 1a in aqueous solution is shown on the graph below: 1) 1.0 Fraction of species 1332333333 H) H) 0.9 D.R 0.7 gos 8 as 0.3 82 0.1 OD 0.0 H₂N 2.0 LOH 1a S 4.2 40 180 120 CERER 0.6 04 Total Charge 0.2 34 46 -48 -LD 140 The red line shows the average total charge on each molecule in solution (right axis), while the green, blue and yellow lines show the fraction of each of three differently ionized forms of 1a (left axis). For each of the three forms, draw the structure and give the formal charge. 16 marks] From the graph, estimate the isoelectric point, pl, of 1a, and explain how you arrived at your result. [2 marks] Estimate the pk, of the carboxylic acid group (-COOH) and ammonium group (-NH₂) in 1a and explain how you arrived at your result (4 marks c) For both of the TWO dipeptides that can result from the reaction between zwitterions of 1a and alanine: Give the name of the dipeptide. [2 marks] Give the one and three-letter sequence for the dipeptide. (4 marks) Draw the structure of the dipeptide. (4 marks