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University of Toronto St. George
Michael Baker

Prep101 http:www.prep101.comfreestuff Biochemistry 210 Practice Midterm 1. At physiological pH (7.4) the peptide Tyr-Tyr-Lys-Leu-Pro-Gly-Gly-Leu-Glu-Met-Ser-Ser- Trp-Pro-Val-Phe-Tyr-Lys-His-Arg-Thr-Thr-Val-Val-Leuhas an overall charge of: a) -1 b) 0 c) +2 d) +3 ANSWER: C 2. In the ,-helical peptide: Ala-Ser-Phe-Lys-Pro-Ile-Trp-Leu-Asp-Met-Thr-Try-Ile, the amide N-H proton of the Trp residue is H-bonded to the backbone carbonyl oxygen atom of: a) Phe b) Thr c) Met d) Lys ANSWER: A 3. The tertiary structure of many globular proteins contains extensive unstructured or random regions. Which of the following statements regarding those unstructured regions is CORRECT: a) ,-helix and --sheet residues must be present in equal amounts b) They contain sterically unfavorable backbone rotational angles that destabilize the protein c) They are averaged out in the protein because they convert rapidly between ,-helix and -- sheet d) They consist largely of short (1-2) residue segments with ,-helix and --sheet angles, which are not enough to form a well-defined element of secondary structure. ANSWER: D 4. Under the principle of hydrophobic effect, what would you happen if you added two droplets of water into a beaker filled with the hydrocarbon Heptane: a) Water molecules will be surrounded by heptane molecules b) The two water droplets will remain separate in heptane c) Heptane will break up into thousands of tiny droplets d) The two water droplets will coalesce to form one larger water droplet ANSWER: D Page 1 of 13 Prep101 http:www.prep101.comfreestuff 5. By observing a Ramachandran plot of a protein in which it is not known which points correspond to which amino acids along the protein sequence it can be determined that: a) The percentage and position of unstructured regions in the protein sequence b) The number and position of ,-helices in the protein c) The backbone rotational angles of the protein chain and the types of secondary structure(s) present in the protein d) The rotational angles of the amino acid side chains and the types of secondary structure(s) present in the protein ANSWER: C 6. If you were to restore heat-denatured collagen to native-like collagen rather than to produce gelatin, the best way would be to: a) Keep shaking the flask after adding artificial flavouring and colouring to the mixture b) Heat-denature under concentrated conditions followed by very slow cooling of the solution c) Heat-denature under dilute conditions followed by rapid cooling of the solution d) Heat-denature under dilute conditions followed by very slow cooling of the solution ANSWER: D 7. Among the following which conclusion can not be made from the results of the Anfinsen experiment involving refolding of ribonuclease: a) The correct H-bonding interactions do not take place in refolding ribonuclease in the presence of urea b) Before the H-bonding interactions can take place, native disulfide bonds must be re- formed c) In order for the protein to re-fold to its native conformation, side chain-side chain H- bonding interactions must form correctly d) The secondary and tertiary structure of ribonuclease is determined by primary sequence ANSWER: C -1 8. The ob-1rvation that --sheets have a lower Amide I frequency (1620 cm ) than ,-helices (1650 cm ) in an infra-red (IR) spectrum indicates that: a) ,-helix H-bonds are weaker than the -sheet H-bonds b) --sheet carbonyl groups point in the opposite directions along a --sheet strand c) An ,-helix is shorter than the --sheet strand, which has the same number of amino acids d) Peptide carbonyls in --sheet are further away from their N-H partners in --sheets than in ,-helices, the weakening the H-bonds Page 2 of 13
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