Spring 2016 Test 4A may participate in enzymaticaly catalyzed reactions by which

Question

Spring 2016 Test 4A may participate in enzymaticaly catalyzed reactions by which of the following? hem properly for reaction a By binding to substrates to help orient them propery for reaction b By promoting 7. Metal ions oxidation-reduction reactions c. By shielding negative charpes of the substrate or active site. d. By enchancing the nucleophilicity of water e. Metal jons may contribute to catalysis by all the ways mentioned above organic r Metal ions are unimportant in enzyme-catalyzed reactions and only serve as inorg catalysts 8. During the catalytic mechanism of serine proteases, an increase in hydrogen bonding between the tetrahedral intermediate and amino acid residues in the oxyanion hole" is an example of a. general acid-base catalysis. b. covalent catalysis. c. metal ion catalysis d. preferential binding of the transition state e. enzyme inactivation. 9. Which of the following is NOT a mechanism that keeps pancreatic proteases from acting on the cells that synthesize them? a. Synthesis of naturally occurring protease inhibitors. b. Synthesis of proteases as inactive precursors, which are later activated by proteolysis. c. Phosphorylation of proteases thereby inactivating them d. Sequestration of proteases in exocytotic vesicles 10. As applied to the Michaelis-Menton equation, the steady-state assumption states that: a. The concentration of substrate is constant as a function of time. b. The concentration of product is constant as a function of time c. The concentration of enzyme-substrate complex is constant as a function of time All of the above are true. d. e None of the above is true. 11. For an enzyme that obeys Michaelis-Menton kinetics, Ka is a, equal to [S] when Vo·Shu. b. a relative measure of the velocity of an enzyme. c. a relative measure of the substrate affinity of an enzyme d. a relative measure of the catalytic efficiency of the enzyme. e. both a and c are true f. both b and d are true all of the above are true. none of the above is true g. h. 12. A given enzyme has a K of 0.50 mM and a Vmax of 5.0 mM/'s when the total enzyme concentration of 5.0 x 10 M. Which of the following is true?

Explanation / Answer

I will only answer question 12, because I have no knowledge of the theory of the enzymes. I apologize for that. However, I do know the expression to get Km, kcat and Vmáx, so I can answer this question. I recommend to you to post the rest of your questions again in a different post, so you can get answered for those questions.

First to get the value of kcat, we need to use the following expression:

Vmáx = kcat[E] ---> solving for kcat we have:
kcat = Vmáx/[E]

kcat = 5x10-3 M/s / 5x10-6 M = 1000 s-1 or simply 1x103 s-1.

With this value we can discart option a) and c), let's calculate now the relationship of kcat/Km:
kcat/Km = 1x103 s-1 / 0.5x10-3 M = 2x106 s-1 M-1

Option D is the correct option.

Hope this helps

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