TBR: Metabolic Components - Error in Passage 1 diagram???

[Gauss44]

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The Berkeley Review
Metabolic Components Section 7
Passage 1

Question 1.

Shows a diagram with what looks like equilibrium half arrows an enzyme with an inhibitor attached and without an inhibitor attached. I took this to mean that it's a competitive inhibitor. It looks like the inhibitor detaches from the substrate.

Then the answer key says it's suppose to be non-competitive. Can anyone explain this diagram to me??? Or is it an error? Thanks.

 

[sakabato93]

Does the inhibitor detach from the active site, or from a different site on the enzyme molecule?

 

[Gauss44]

Does the inhibitor detach from the active site, or from a different site on the enzyme molecule?

A different site. Now that you mention it, I think you figured it out. That's what makes it non-competitive.

I still want to know why the arrows look the way they do. Do equilibrium arrows have another meaning?

 

[catzzz88]

The arrows at the top and bottom of the square are simply saying that the substrate (S) can either attach to the enzyme from its free form, or (if already attached), it can detach from the enzyme and become free form.

The arrows on the left and right of the square say that the inhibitor can attach or detach, yes. The inhibitor is not necessarily permanently bound to the enzyme.

 

[Gauss44]

The arrows at the top and bottom of the square are simply saying that the substrate (S) can either attach to the enzyme from its free form, or (if already attached), it can detach from the enzyme and become free form.

The arrows on the left and right of the square say that the inhibitor can attach or detach, yes. The inhibitor is not necessarily permanently bound to the enzyme.

A non-competitive inhibitor is not necessarily permanently bound?

 

[catzzz88]

A non-competitive inhibitor is not necessarily permanently bound?

Absolutely not! In fact, the most common kinds of biological non-competitive inhibition are reversible. This is one of many great ways for the body to regulate metabolic processes.

Best,
C