1. State whether the following statements are true or false. i) An enzyme cataly
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Question
1. State whether the following statements are true or false.
i) An enzyme catalyst DOES alter the equilibrium constant for a reaction.
2. True or False?
Due to transition state stabilization, the enzyme proline racemase would be predicted to bind to an intermediate with a tetrahedral carbon at the reaction site rather than a trigonal planar carbon.
3. An enzyme is found to produce -OH as a nucleophile from water during the mechanism of the catalyzed reaction. Which would NOT be a good candidate in the enzyme for the molecule primarily responsible for the formation of this -OH?
A) a deprotonated Ser in the active site
B) Zn2+
C) a deprotonated His in the active site
D) a Val in the active site
4. What is the best description of the "oxyanion hole" generated during the mechanism of a serine protease - catalyzed reaction?
A) the oxyanion hole describes the stabilization of the tetrahedral intermediate where H-bonding lowers the energy of the negatively charged oxygen resulting from nucleophilic attack on the carbonyl carbon
B) the oxyanion hole describes the planar enzyme-substrate intermediate formed as the carbonyl double-bond is reformed.
C) the oxyanion hole is generated as a result of deprotonation of the serine by a neighboring histidine, resulting in a negatively charged oxygen nucleophile
D) the oxyanion hole describes the binding pocket for the phenylalanine amino acids that are preferred substrates for the serine proteases
5. Which statement describes a common feature of both the RNase A and Serine Protease mechanisms?
A) Water is protonated by a Histidine to generate an acidic hydronium ion.
B) A deprotonated serine acts as a nucleophile
C) a covalent enzyme-substrate intermediate is formed
D) a Histidine acts as a Bronsted base to remove a proton from an alcohol group.
i) An enzyme catalyst DOES alter the equilibrium constant for a reaction.
ii) The presence of an enzyme catalyst DOES NOT decrease the energy required to reach the transition state. iii) An enzyme catalyst DOES affect the rate of a biochemical reaction. iv) The presence of an enzyme catalyst DOES NOT decrease the change in free energy (Gfinal - Ginitial) of the overall reaction.Explanation / Answer
Answer 1)
i) An enzyme catalyst DOES alter the equilibrium constant for a reaction. True
ii) The presence of an enzyme catalyst DOES NOT decrease the energy required to reach the transition state. False
iii) An enzyme catalyst DOES affect the rate of a biochemical reaction. True
iv) The presence of an enzyme catalyst DOES NOT decrease the change in free energy (Gfinal - Ginitial) of the overall reaction. False
ANSWER 2)
Due to transition state stabilization, the enzyme proline racemase would be predicted to bind to an intermediate with a tetrahedral carbon at the reaction site rather than a trigonal planar carbon. False
Answer 3)
Zn+2
Answer 4)
the oxyanion hole describes the stabilization of the tetrahedral intermediate where H-bonding lowers the energy of the negatively charged oxygen resulting from a nucleophilic attack on the carbonyl carbon.
Answer 5)
Water is protonated by a Histidine to generate an acidic hydronium ion.
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