Practice MT Ans

5 but not at ph 45 in 2 d gel electrophoresis protein

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Unformatted text preview: lectrophoresis, Protein B ceases migration when it reaches a pH = 6.0 in the1st dimension. Protein C is displaced from carboxymethylcellulose by Na+ at pH = 6. Using this information, answer the following questions. Write “D” if there is not enough information provided to answer the question. (i) Which protein is expected to elute first when the sample is applied to a size exclusion column? Answer: D (ii) Which protein has the highest pHI (pI) value? Answer: C (c) The slope of a semi log graph relating polypeptide molecular mass to distance of migration during SDSPAGE is -0.5 cm-1. If a polypeptide with a moelcular mass of 20,000 Daltons migrates 3.4 cm, how far does a polypeptide with a molecular mass of 9,000 Daltons migrate in the same gel? log 20,000 = 4.30 log 9,000 = 3.95 4.30 - 3.95/3.4 - x = -0.5 cm x = 4.1 cm Question #11 (16 points) This is the enzyme mechanism that WILL BE examined on the actual, real BIOL201 Midterm Exam-I to be held on Feb. 10, 2010 @ 7:00 PM. BIOL 201 TAs have been instructed NOT to answer questions about this mechanism! NOTE! READ the instructions at the bottom of the page. For full credit you need to draw molecular structures to illustrate you answer. The following diagram shows a mechanism for the enzyme-catalyzed hydrolysis of an amide (linkage) in the dipeptide substrate R1-R2. “His-X” and “Glu-Y” are two residues in the active site of the enzyme. The thick arrow indicates a tetrahedral intermediate resembling the two transition states for the reaction. His-X Glu-Y Answer the two questions on p.12 about how the enzyme increases the rate at which the peptide linkages are hydrolyzed in aqueous solution. For full credit, it WILL BE necessary to draw some relevent molecular structures to illustrate your answers. See next page. (a) Explain....................................... (8 points: 4 points for explanation, 2 points each for 2 structures) (b)Explain....................................... (8 points: 4 points for explanation, 2 points each for 2 structures)...
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