2005mcb200f1

2005mcb200f1 - University of Cape Town Department of...

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University of Cape Town Course Code: MCB200F Course Name: Intro to Biochemistry Paper: 1 Date: 10 June 2005 No.of pages: 14 Marks:130 Time: 3 Hours Venue: DO 1 - 09h00 ANSWER ALL THE QUESTIONS In the interest of economy please write on both sides of the exam script Please answer each section in a different answer book. Section 1 Dr Jerry Rodrigues 71 Marks MCB200F June Examination 2005 Section A (Amino acids and proteins – 28 marks) 1. Shown below is the curve for 50 mL of an amino acid solution titrated with 1.0 M NaOH solution starting from the zwitterionic form of the amino acid . (a) Mark clearly on the graph the position of the pI, the pKa values and the equivalence points. [5] (b) What amino acid was titrated? [1] (c) Calculate the concentration of the amino acid in the solution. [2] (8) 2. Offer a reasonable explanation as to why valine and isoleucine occur more frequently in β -strands than in α -helices. (2) 1
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Questions 3 to 7 are of the multiple choice type (select the best answer). 3. Identify the peptide with the highest extinction coefficient at 280nm, ie. the one that would absorb the greatest amount of UV radiation at a wavelength of 280 nm assuming equal concentration. A. Y-E-D-R-F-W B. R-N-Y-F C. Y-H-L-I-V-L-H-I D. G-G-A-F E. They would all absorb the same amount of UV radiation at 280 nm. (1) 4. Which pair of amino acid residues might be involved in a salt bridge in a protein? A. glycine and methionine B. glutamate and lysine C. leucine and alanine D. serine and asparagine E. glutamine and cysteine (1) 5. In the water-soluble globular protein structure shown below, the amino acid residue in the following list that would, most likely, be found on the side of an α -helix facing towards the β -sheet portion of the structure is: (1) 6. Select the 15-amino acid polypeptide sequence below, that is most likely to be in an amphipathic α -helix on the surface of a water-soluble protein: (make use of the helical wheel provided to help you decide) A. H-A-S-I-K-F-R-M-N-L-H-A-S-V-A B. C-T-R-K-G-S-Q-Y-T-G-D-H-E-S-P C. L-M-R-T-I-G-S-V-A-T-C-F-A-D-S D. V-A-M-W-F-I-V-Y-N-H-R-K-S-G-D E. All of the above would be equally likely 2 A. Glutamate B. Serine C. Lysine D. Asparagine E. Leucine
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(3) 7. A change in a protein’s 3-D shape or conformation due to disruption of hydrogen bonds, disulfide bridges and ionic bonds is termed: A. renaturation B. stabilization C. hydrolysis D. destabilization E. denaturation (1) 8. The hemagglutinin protein in influenza virus contains a remarkably long α -helix, with 53 residues. (a) How long is this α -helix (in nm)? (b) How many turns does this helix have? (c)
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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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2005mcb200f1 - University of Cape Town Department of...

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