Which of the following statements regarding enzyme catalysis is false? All options are false. Once formed, the transition state slowly proceeds to forming the product at a rate determined by cofactor binding The free energy of binding of the enzyme to the transition state is more favorable than the free energy of binding of the enzyme to the substrate The substrate and active site of the enzyme are solvated to promote enzyme-substrate interaction Once formed, the product dissociates from the enzyme after ATP hydrolysis in order to regenerate the active site

Which of the following statements regarding enzyme catalysis is false? All options are false. Once formed, the transition state slowly proceeds to forming the product at a rate determined by cofactor binding The free energy of binding of the enzyme to the transition state is more favorable than the free energy of binding of the enzyme to the substrate The substrate and active site of the enzyme are solvated to promote enzyme-substrate interaction Once formed, the product dissociates from the enzyme after ATP hydrolysis in order to regenerate the active site

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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When enzyme solutions are heated, there is a progessive loss of catalytic activty over time due to denaturation of the enzyme. A solution of the enzyme hexokinase incubated at 45 degrees Celsius lost 50% of its activity in 12 minutes, but when incubated at 45 degrees Celsius in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity in 12 minutes. Suggest why thermal denaturation of hexokinase was retarded in the presence of one substrates.
Which of the following is TRUE concerning the induced fit model of enzyme catalysis? * (One correct answer only) A. The active site can be influenced by molecules binding elsewhere on an enzyme B. The initial binding of enzyme and substrate is the most tightly bound conformation C. The induced fit must occur prior to the initial binding of enzyme and substrate in order for the reaction to proceed D. The binding of enzyme and substrate is weakest in the transition state
When enzyme solutions are heated, there is a progressive loss of catalytic activity over time due to denaturation of the enzyme. A solution of the enzyme hexokinase incubated at 450C lost 50% of its activity in 12 minutes, but when incubated at 450C in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity in 12 minutes. Suggest why thermal denaturation of hexokinase was retarded in the presence of one substrates
When enzyme solutions are heated, there is a progressive loss of catalytic activity over time due to denaturation of the enzyme. A solution of the enzyme hexokinase incubated at 45 °C lost 50% of its activity in 12 min, but when incubated at 45 °C in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity in 12 min. Suggest why thermal denaturation of hexokinase was retarded in the presence of one of its substrates.
During chymotrypsin-mediated catalysis, which of the following statements is true? Select any/all answers that apply. A. A basic (positively-charged) side chain of the substrate polypeptide sits within the oxyanion hole of the enzyme. B. A basic (positively-charged) side chain of the substrate polypeptide sits within the specificity pocket of the enzyme. C. Ser195 hydrogen-bonds with the backbone carbonyl group of the substrate polypeptide within the oxyanion hole of the enzyme. D. All three residues that comprise the catalytic triad of the enzyme interact directly with the substrate polypeptide chain. E. Both covalent catalysis and acid-base catalysis occur.
In _____________ inhibition, the EI complex readily dissociates and the enzyme is again available for substrate binding.
Several factors contribute to enzyme catalysis. What arethey? Briefly explain the effect of each.
An example of an enzyme-catalyzed reaction proceeding via a transition-state stabilization mechanism is the hydrolysis of peptides by chymotrypsin while, Lysozyme is often cited as an example of an enzyme which operates by strain mechanism. Discuss both mechanisms in the context of each enzyme.
Which of the following statements regarding enzymes and transition states is true? stabilization of the transition state must be less than stabilization of ES for catalysis to occur binding of substrate to an enzyme often causes strain, thus promoting transition state formation the transition state conformation of an enzyme catalyzed reaction is identical to the conformation seen in the uncatalyzed transition state formation of the transition state always assures that the reaction will proceed to product none of the above are true
Regarding the physical condition (characteristics of the solution/environment) in which an enzyme finds itself: sometimes enzymes are most active at a certain level and still active but to a lesser degree at a level above or below the optimal level. Describe the likely reason for the enzyme’s decrement in function at levels other than the optimal level?
Given the following data in enzyme-catalyzed reaction, what are the Vm, Km of with DEDS (presence of inhibitor) and without DEDS ( absence of inhibitor) and its type of inhibition.
At what substrate concentration would an enzyme with a kcat of 25.0 s-1 and a KM of 3.5 mM operate at 25% of its maximal rate? How many reactions would the enzyme catalyze in 45 seconds when it is fully saturated with substate, assuming the enzyme has one active site?