Mcat biochem Enzyme Kinetics PDF

Preview

Summary

Professor: Dr. Heather Tienson-Tseng
MCAT Enzyme Kinetics...

Description

Lineweaver Burk Tuesday, October 12, 2021

12:22 PM

Enzyme Kinetics ◊

◊

◊

Reaction rate is V - velocity ○ Mol/s ○ Depends on concentrations of substrate and enzyme § In biological systems, enzyme concentration is somewhat constant and [S] is the only variable we consider ○ V is directly proportional to S quantity (double S, V is doubled) ○ Vmax is the reaction rate when the enzyme is saturated § All the active sites are occupied and the enzyme stops responding to increased [S] Michaelis constant Km ○ The substrate concentration at which reaction velocity is half the maximum § Found by Vmax/2 ○ This value is unique for each enzyme-substrate pair ○ Gives information of affinity of enzyme's active site § Low Km = high affinity □ Not much substrate is required to get the reaction rate to half of the maximum, so the enzyme has a high affinity ○ Look at this as enzyme affinity for MCAT problems Cooperativity ○ In multiple subunit enzymes or enzymes with multiple binding sites, the binding of one substrate to a subunit affects the affinity of the other subunits § Positive cooperativity- binding of a substrate to one subunit increases the affinity of the other subunit □ Previous conformation before binding was tense, and then it becomes relaxed § Negative cooperativity- binding of a substrate to one subunit decreases the affinity of the other subunit ○ This phenomenon results in a sigmoidal curve between [S] and V § At low [S] enzyme has low affinity § Steep increase in reaction rate as enzyme enters relaxed state

○

§ Steep increase in reaction rate as enzyme enters relaxed state § Vmax reached - saturation Ex. Hemoglobin's binding also follows a sigmoidal curve

Lineweaver-Burk Plot

-

-

In y=mx+b form ○ Slope of the graph is Km/Vmax ○ Y-intercept is 1/Vmax ○ X-intercept is -1/Km Know how a change in any of the values or the addition of a certain inhibitor would change shape of plot...