Biochemistry: competitive inhibition

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Joined: Tue Jun 06, 2017 10:18 pm

Biochemistry: competitive inhibition

Postby jkwdo12 » Fri Dec 29, 2017 9:07 pm

Hi, I am running into some trouble in understanding the concept of competitive inhibition. From what I know is that the competitive inhibition does not affect the Vmax. However, I also found out that the competitive inhibition can decrease the rate of reaction. Isn't the rate of reaction equivalent of Velocity of reaction? Since the Vmax is not affected by the competitive inhibition, how can the rate of reaction be altered by the competitive inhibition?

I am confused..... I want to say thank you in advance for clarifying this for me... :D
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Re: Biochemistry: competitive inhibition

Postby NS_Tutor_Andrew » Tue Jan 02, 2018 1:02 pm

Hi jkwdo12,

Thanks for the excellent question! The key here is understanding that Vmax refers to the maximum rate of a reaction for a given concentration of reactants and enzyme. The idea basically is that the rate will increase as you keep adding substrate, up to a certain point where there is just so much substrate that the enzyme is completely saturated and is working at 100% capacity. At any given substrate concentration, the reaction rate will be lower if you add a competitive inhibitor, but if you add enough substrate, you can basically "drown out" the effects of the inhibitor.

To see this point, take a look at the attached Michaelis-Menten graph. At any given point on the x-axis, the rate of the reaction with the inhibitor will be lower, but if we were to go far enough to the right (not fully shown on the graph), the red and blue lines would eventually converge.

Hope this helps clarify things, and Happy New Year!
Andrew D.
Content Manager, Next Step Test Prep.

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