A new antibiotic has been developed. It acts as a noncompetitive inhibitor. How will this antibiotic affect delta G for the enzyme-catalyzed reaction?

Question

A.  Delta G will increase
B.  Delta G will decrease
C.  Delta G will be unaffected


Clarify Question
What is the key concept addressed by the question?
What type of thinking is required?

  Gather Content
  What do you already know about enzymes and free energy? What other information is related to the question?

  Choose Answer
Do you have all necessary information to analyze how the noncompetitive inhibitor might influence free energy?   

  Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

C.  Delta G will be unaffected

Clarify Question
What is the key concept addressed by the question?
        · The question asks you ascertain how an antibiotic that noncompetitively inhibits an enzyme will affect the reaction’s change in free energy.    
What type of thinking is required?
        · You are being asked to break down, or analyze, how a noncompetitive inhibitor antibiotic will influence an enzyme-catalyzed change in free energy.    

  Gather Content
  What do you already know about enzymes and free energy? What other information is related to the question?
        · Remember that an enzyme helps to accelerate the rate of a reaction by making the reaction more likely to occur. Recall that noncompetitive inhibitors bind not to the active site, but to an enzyme’s secondary site which changes the protein’s three-dimensional confirmation, changes the shape of the active site, and thereby reduces the overall speed of the reaction.
        · Considering the structure and function of enyzmes and how noncompetitive inhibitors work, how might the free energy of the reaction be affected?

  Choose Answer
Do you have all necessary information to analyze how the noncompetitive inhibitor might influence free energy?   
        · Recall that noncompetitive inhibitors bind to a secondary site on the enzyme, which changes the shape of the enzyme and precludes the substrate from binding to the active site. Thus, no amount of substrate will allow the enzyme to reach its top speed because the shape of the active site has been changed.
        · Regardless of how fast the enzyme can process the reaction (meaning with or without the noncompetitive inhibitor), the actual difference in free energy between the reactants and the products will not change. Whether or not a reaction is exergonic or endergonic is a function of whether or not the reaction has a positive or negative delta G. The presence of an enzyme, or a noncompetitive inhibitor, has no effect on the difference in free energy. As a result, the noncompetitive inhibitor antibiotic should have no effect on the free energy required for the enzyme-catalyzed reaction.  

  Reflect on Process
  Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        · This question asked you to analyze the effect of a noncompetitive inhibitor antibiotic on the free energy for an enzyme-catalyzed reaction.       
        · If you got the answer correct, well done! If you got an incorrect answer, did you remember that noncompetitive inhibitors bind to a secondary site on an enzyme? Did you recall how noncompetitive inhibitors affect overall reaction rate as substrate concentration changes? Were you able to determine that free energy, or the difference in free energy from reactants to products, doesn’t change regardless of the presence or absence of a noncompetitive inhibitor?