Prelim 1 Fall07 Key - 1. (2 points) Using structures, write...

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1. (2 points) Using structures, write a balanced chemical equation for the hydrolysis of an ester. HOH + RCOOR' RCOOH + R'OH 2. (2 points) The pK of an acid is always: (Circle all correct answers) a. equal to the pH at which it carries a positive charge. b. equal to the pH at which it carries a negative charge. c. equal to the pH at which it carries no net electric charge. d. a function of the pH of the solution which contains the acid. e. equal to the pH at which it is half dissociated. 3. a. (4 points) Write the structure of asparagine at pH = 7.0. (Nelson & Cox, p. 79) b. (2 points) Give the three letter abbreviation of an amino acid that has a side chain with each of the following properties. non-polar - Ala (alanine), Phe (phenylalanine), Gly (glycine), Ile (isoleucine), Leu (leucine), Pro (proline), Val (valine), Tyr (tyrosin), Met (methionine), Cys (cysteine), Trp (tryptophane) sulfur-containing, never charged - Met (methionine) (3 points) Give the one letter abbreviation of an amino acid that has a side chain with each of the following properties. polar, never charged - N (asparagine), Q (glutamine), S (serine), T (threonine) negatively charged at pH 7 - E (glutamic acid), D (aspartic acid) ionizable, but uncharged at pH 7.0 - C (cysteine), H (histidine), Y (tyrosine) c. (1 point) Name the amino acid that will have the strongest buffering power at pH 6. Histidine d. (2 points) Calculate the isoelectric point of aspartic acid. (Nelson & Cox, pp. 84-5) (2.0 + 3.9) / 2 = 2.95
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BioBM 330 prelim 1, Fall '07 ANSWER KEY page 2 4. a. (2 points) After a protein is synthesized, amino acids in a protein are sometimes modified. Name two ways in which they are commonly modified. (Nelson & Cox, Table 3-4, p 88 ) phosphorylation, carboxylation, methylation, glycosylation (carbohydrate addition), isoprenylation, etc. b. (1 point) Name the analytical technique most often used by biochemists to identify these types of modifications. (Nelson & Cox, Box 3-2, pp. 102-4 and Study Guide, Unit 2, page 13) Mass Spectroscopy 5. (2 points) Briefly describe the importance of protein disulfide isomerase in protein folding. PDI catalyzes the shuffling of disulfide bonds until the bonds of the native conformation are formed and thus eliminates intermediates with inappropriate disulfide cross links. 6. (4 points) Define and clearly differentiate between each of the following pairs of terms. a. polyclonal & monoclonal antibodies (Nelson & Cox, p. 180) Polyclonal antibodies are a mixture of antibodies from animal blood that recognize different regions (epitopes) on a single antigen molecule. In contrast monoclonal antibodies, made in vitro , recognize a single region on the antigen. b.
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This note was uploaded on 04/06/2008 for the course BIOBM 3300 taught by Professor Blankenshi during the Fall '08 term at Cornell University (Engineering School).

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Prelim 1 Fall07 Key - 1. (2 points) Using structures, write...

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