biochemistry questions

Question

20. Which of the following mechanisms of allosteric enzymes activation is correct?

a	They induce the denaturation of an apoenzyme
b	They block the enzyme active centre
c	They change the spatial configuration of the enzyme active centre
d	They oxidize sulfhydryl group of the enzyme active center

21. What is the inactive form of a proteolytic enzyme?

a	Apoenzyme
b	Coenzyme
c	Proenzyme
d	Isoenzyme

22. What is the mechanism of competitive inhibitors action?

a	They block the enzyme active centre
b	They induce the denaturation of an apoenzyme
c	They alter spatial configuration of an enzyme active centre
d	They oxidize sulfhydryl groups of an enzyme active centre

Answer 1

20) An allosteric site on an enzyme, is anywhere other than the active site. Usually molecules will bind to the allosteric site & cause a conformational change to the enzyme. This conformational change can turn the protein on via activation, or turn it off via inhibition. Therefore answer C is the best choice.

21) Proteolytic enzymes are very useful for digesting proteins, however it would be dangerous to have them active all the time, since they could breakdown all of the proteins present. This is why they usually have an inactive precursor. This form of inactive precursor is called a zymogen, or a proenzyme, so C is the best answer. They are easy to recognize by their name ending in -ogen. For example, trypsinogen, fibrinogen, pepsinogen.

22) Competitive inhibitors are characterized by binding to the active site before the substrate/reactant can bind. Therefore the inhibitor COMPETES for the active site. A is the best answer.

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