2001mcb200f2 - University of Cape Town Department of...

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University of Cape Town MCB200F : Introduction to Biochemistry Paper 2 June 2001 Time: 3 hours Marks: 139 ANSWER ALL THE QUESTIONS In the interest of economy please write on both sides of the exam script Please answer each lecturer’s questions in a different answer book. Graph paper will be provided. Section 1 J Rodrigues (35 marks) 1. What is the pI of a monoamino, dicarboxylic acid for which: pKa 1 = 2.2, pKa 2 = 4.4 and pKa 3 = 9.7? (1) 2. The dissociation constant of propionic acid is 1.33 X 10 -5 M. What is the pKa? (2) 3. The pKa of acetic acid is 4.76. If 25% of the acetic acid in a 0.1 M solution is in the protonated state, what is the pH of the solution? (3) 4. Draw the titration curve for the amino acid Arginine (pKa 1 =1.82, pKa 2 =8.99, pKa 3 =13.2). On the same graph label the following points: pKa’s, the pI and all the pH regions at which Arg would act effectively as a buffer. (7) 5. Before Anfinsen carried out his work on the refolding of ribonuclease, some scientists argued that instructions for folding are given to the protein during its biosynthesis. (a) How did Anfinsen’s experiments contradict that argument? (b) Did Anfinsen’s finding apply to all proteins? Why? (6) 6. Describe the principles involved in the separation of proteins by ion-exchange chromatography (be specific) according to the following headings: (a) Anion- and cation-exchange resins (pKa’s etc). (b) The importance of the pH of the buffers.
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This note was uploaded on 01/05/2011 for the course BLY 440 taught by Professor Williams during the Fall '10 term at Alabama.

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2001mcb200f2 - University of Cape Town Department of...

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