Kinetics (3) Flashcards
Semester 1 year 1
In a binding (saturation) curve, what are the x and y axis?
-x axis = [L]/um
-y axis = [PL]/[P]T
On a binding curve, where is Kd?
At the point on the x axis when [PL]/[P]T is at 0.5
What happens to the curve on a binding curve when [L] becomes greater than Kd?
The curve levels out
Describe the curve of an enzyme graph of rate of product formation against substrate concentration
-as substrate conc. increases, rate increases at first
-at very high substrate conc. the curve plateaus
-the rate is independent of substrate conc., so is a 0 order reaction
What is the plateaued point of a rate against substrate conc. graph called?
The Vmax
What is the 2 step equation to go from enzyme and substrate to enzyme and product?
E + S ⇌ ES ⇀ E + P
Why do we assume we have a very low concentration of enzyme in relation to substrate?
-makes reaction slow enough to follow on lab equipment + is cheaper
-as [E] is low compared to [S], then [ES] is low, so can assume [S] free = [S] total
What does the Michaelis Menten equation describe?
-kinetic behaviour of E + S ⇌ ES ⇀ E + P
-equation is for rate of reaction
How can ES ⇀ E + P be modelled?
-as a unimolecular irreversible reaction
-just need a rate constant - Kcat
How can you calculate the rate for ES ⇀ E + P?
rate = Kcat x [E]total x {[S] / ([S] + Km)}
or rate = Kcat x [ES]
What is Km?
-the Michaelis constant
-in general, it’s not a binding constant
How do you calculate Km?
-concentration of substrate at 1/2 Vmax
-like Kd
How do you calculate Vmax?
Kcat x [E]total
What is Kcat?
-the first order rate constant
-catalytic constant/turnover number
What is the Michaelis Menten equation?
Rate of product formation = (Vmax x [S]) / ([S] + Km)
