BIBC102 Fall 2008 Midterm 1 Key

BIBC102 Fall 2008 Midterm 1 Key - Metabolic Biochemistry...

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Metabolic Biochemistry KEY Fall Quarter 2008 Midterm Exam 1 (270 pts.) EXAM A 1) (18 pts) The structure of the amino acid, threonine, is shown below. For each of the following, circle each atom in , and clearly label: a. the alpha-carbon; b. the alpha- amino group; c. the R-group. 6 pts. each 2) (6 pts.) The amino acid shown in question 1 would be considered: (check one) a. Hydrophobic ____ b. Positively charged ____ c. Polar X d. Aromatic ____ 3) (12 pts.) For the following freely reversible chemical reaction, write the net reverse velocity (-v) in terms of the rate constants and reactant/product concentrations. A + B C -v = k -1 [C] – k 2 [A][B] (6 pts. forward rxn., 6 pts. reverse rxn.) 4) (20 pts.) How does enzymatic catalysis affect the rate constant (k) for the reaction being catalyzed? Explain. (Three sentences or less ) Enzymatic catalysis decreases the activation energy (8 pts.) for the reaction. A small (2 pts.) decrease in the activation energy produces a large (4 pts.) increase (6 pts.) in the rate constant . 5) (20 pts.) How does enzymatic catalysis affect the equilibrium constant for the reaction being catalyzed? Explain. (Three sentences or less) Enzymatic catalysis has no effect on the standard free energy change (8 pts.) for the reaction. The standard free energy change determines the equilibium constant (2 pts.) , so the enzyme has no effect on the the equilibrium constant (10 pts) . CH 3 C - O CH H 3 N + H OH k 2 k -1 a. b. c.
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6) (8 pts.) Two substrates bind to the active site of an enzyme and are spatially oriented such that the reactive chemical groups on each substrate are lined up next to each other. Would this more likely affect the enthalpy component or the entropy component of the free energy of activation needed to reach the transition state? (You don’t need to explain why.) The entropy component 7) (12 pts.) For each description given below, write in all of the following terms that most likely apply to that inhibitor.
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This note was uploaded on 02/06/2009 for the course BIBC BIBC 102 taught by Professor Price during the Fall '08 term at UCSD.

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BIBC102 Fall 2008 Midterm 1 Key - Metabolic Biochemistry...

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