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Biology
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13 Dec 2019

Which of the following is a primary function of the active site of an enzyme? a.) It binds noncompetitive inhibitors of the enzyme. b.) It catalyzes the reaction associated with the enzyme. c.) It is activated by the presence of the end product of the metabolic pathway in which the enzyme is involved.

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Related questions

45. The catalysis mechanism used by lysozyme to break down bacterial cell walls is

acid–base catalysis.

covalent catalysis.

metal cofactor redox catalysis.

induced strain.

unknown.

46. Competitive inhibitors of enzymes work by

fitting into the active site.

fitting into a site other than the active site.

altering the shape of the enzyme.

changing the enzyme into an inactive form.

increasing the activation energy of the enzyme-catalyzed reaction.

47. Nerve gases such as Sarin and malathion

block specific chemical transformations by inactivating specific enzymes.

have reversible effects on animals.

are proteins with a primary structure.

block the energy coupling cycle of ATP.

bond covalently to the active site of the enzyme.

48. How do competitive and noncompetitive enzyme inhibitors differ?

Competitive inhibitors bind to the active site, whereas noncompetitive inhibitors change the shape of the active site.

Competitive inhibitors have a higher energy of activation than noncompetitive inhibitors have.

They function at different pH values.

Noncompetitive enzyme inhibitors contain magnesium, whereas competitive inhibitors contain iron.

Noncompetitive enzyme inhibitors are reversible, whereas competitive inhibitors are irreversible.

An enzyme (E) catalyzes the following reaction: A+B E C However, the (C) binds to the active site of the enzyme in a reversible fashion and keeps the enzyme from functioning. What happens if A and B are continually added to a solution that contains a fixed amount of the enzyme?

Phosphofructokinase (PFK1) is a glycolytic enzyme that catalyzes the irreversible transfer of a phosphate from ATP to fructose -6-phosphate to form fructose-1, 6- bisphosphate.

fructose-6-phosphate + ATP --> fructose-1,6-bisphosphate + ADP

PFK1 is the key regulatory enzyme for glycolysis. When ATP levels are high in the cell, the cell no longer needs metabolic energy production to occur. In the case of these high energy levels, PFK1's activity is inhibited by allosteric regulation by ATP, which essentially closes the valve on the flow of carbohydrates through glycolysis.

Recall that allosteric regulators bind to a different site on the enzyme rather than the active (catalytic) site. ATP binds to the regulatory site and decreases PFK1 activity. ATP bound in the regulatory site acts as a modulator by lowering the affinity of PFK1 for its substrate, fructose-6-phosphate. AMP on the other hand, which is generated when the cell is in a low energy state binds to allosteric site and increases enzyme activity.

7. The enzyme PFK1 is an example of a non-regulatory enzyme or regulatory enzyme?

8. How is PFK regulated?

A. It is not regulated because it is a non-regulatory enzyme

B. allosteric enzyme regulation

C. covalent enzyme regulation

D. or proteolytic cleavage enzyme regulation?

9. What is the substrate and to which site on the enzyme does it bind? Which compounds are the positive and negative effectors?

10. In which conformational state would the enzyme be when negative inhibitors bind and in which conformational state would the enzyme be when positive inhibitors bind?

11. PFK1 is a heterotropic or homotropic regulatory enzyme?

12. Draw (or insert the picture from your course packet available on Canvas) the graph that corresponds to this reaction. Your graph should include the activity of PFK without bound effectors, with bound positive effector, and with bound negative effector. Label (or describe) each line to distinguish these along with which molecules are positive and negative effectors.

13. How does Vmax and K0.5 change with the positive and negative effectors?

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