Inhibitor constant

[663697]

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Can anybody comment on if Ki is relevant for the MCAT? One of the EK practice passages included it in a table as a distractor so I'm not sure if it's still considered fair game.

 

[aldol16]

It's fair game. The MCAT will define a term if it's not in common scientific usage like the Ki and you would be expected to reason from that. For instance, they might say in the passage, "Ki is the inhibitory constant, which measures the concentration of inhibitor at which reaction velocity is half Vmax," and you would be expected to use that information to answer questions.

 

[663697]

It's fair game. The MCAT will define a term if it's not in common scientific usage like the Ki and you would be expected to reason from that. For instance, they might say in the passage, "Ki is the inhibitory constant, which measures the concentration of inhibitor at which reaction velocity is half Vmax," and you would be expected to use that information to answer questions.

Ah ok. I see that the definition you gave is similar to that of Km, except it's referring to the inhibitor concentration. Nonetheless would it be incorrect to assume they are inversely proportional, since it would depend on the nature of the inhibitor (ie. non-competitive with a low Ki wouldn't increase Km)?

 

[aldol16]

Ah ok. I see that the definition you gave is similar to that of Km, except it's referring to the inhibitor concentration. Nonetheless would it be incorrect to assume they are inversely proportional, since it would depend on the nature of the inhibitor (ie. non-competitive with a low Ki wouldn't increase Km)?

They're not inversely proportional - they don't really relate to one another directly. Just think of them as similar mathematically but with different physical meanings.