MCAT AAMC BB Section Bank #20

[GreatSageDoc]

Hello,

I don't understand why we would look at the initial velocity instead of vmax for competitive inhibition. Wouldn't it be simpler to look at the vmax and see if there is a difference?

Please help.

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[lumya]

Competitive inhibitors have the same Vmax but increased Km compared to uninhibited enzymes. So looking only at the Vmax won't tell you anything.

 

[GreatSageDoc]

Competitive inhibitors have the same Vmax but increased Km compared to uninhibited enzymes. So looking only at the Vmax won't tell you anything.

Thank you so much, I really appreciate it!

 

[JimKimSlim]

In Michaelis-Menten kinetics, you obtain Vmax by measuring the initial velocity of the reaction over increasing substrate concentrations. Vmax = the initial velocity at higher substrate concentration.

 

[GreatSageDoc]

In Michaelis-Menten kinetics, you obtain Vmax by measuring the initial velocity of the reaction over increasing substrate concentrations. Vmax = the initial velocity at higher substrate concentration.

This is making a lot more sense now, Thanks! Just to make sure I got it right, using the high initial Vo would make it so that we can test for both Vmax AND Km inhibited and uninhibited and THEN we know what we are looking at in terms of inhibition no matter what kind it is (e.g. competitive, uncompetitive, noncompetitive)?

 

[JimKimSlim]

Using high initial velocity may not work because if the inhibitor is competitive then Vmax won’t change. You’ll likely be given a lineweaver-Burke plot to tell them apart, so you just gotta remember those. A simple review from your biochemistry textbook should be enough.