MCAT biochemistry: enzyme inhibition
The Crowded Active Site
A competitive inhibitor triples an enzyme's apparent Km. A four-minute film that watches substrate and inhibitor fight for the active site, counts who wins, and straightens the curves into the Lineweaver-Burk plot the MCAT keeps asking about.
This browser has 3D graphics turned off, so the set cannot be drawn. The math and the narration still play.
The problem
An enzyme has Km = 2 mM and Vmax = 100 µmol/min. A competitive inhibitor raises the apparent Km to 6 mM. At [S] = 2 mM, the rate in the presence of the inhibitor is closest to: (A) 50 (B) 33 (C) 25 (D) 17 µmol/min.
25 µmol/min: v = Vmax [S] / (Km,app + [S]) = 100 x 2 / (6 + 2)
