Experiment 10: Enzyme Kinetics Flashcards
What is kinetics?
Kinetics is the brand of science concerned with the rates of chemical reactions.
The rate constant k1 describes which reaction?
E + S —-> ES
The rate constant k-1 describes which reaction?
ES —-> E + S
The rate constant k2 describes which reaction?
ES —-> E + P
Steady state conditions
when the rate of formation and breakdown of ES complex are equal.
Michaelis-Menten plot
refer to slides
Formula for Km
([Et] [S])/([ES]) - [S]
The velocity of the catalyzed reaction at any time is
V = k2 [ES]
When the enzyme is saturated with substrate so that all of it exists as ES complex, the velocity is maximum, Vmax =
k2 [Et]
Km in terms of rate constants
(k-1 + k2) / (k1)
What is Km?
is [S] that produces Vmax/2 and [S] at which half of the enzyme active sites are filled.
Is Km independent of amount of enzyme?
yes
Michaelis-Menten Equation
V = Vmax [S]/([S] + [Km])
Is Vmax independent of amount of enzyme?
No, Vmax depends on the amount of enzyme.
Lineweaver-Burk Plot
1/V = (Km/Vmax)(1/S) + 1/Vmax
Inhibitors
are small molecules or ions that can inhibit enzymes by binding.
Competitive Inhibitors
compete with substrates for the active site.
Non-competitive Inhibitors
bind to enzymes at the same time as substrates but at different binding sites.
M-M plot for competitive inhibition
As the inhibition increases higher substrate is needed to overcome the inhibition.
M-M plot for non-competitive inhibition
can not be overcome by increasing the substrate concentration, Vmax cannot be reached.
LB plot how to find Km and Vmx
x-intercept: -1/Km
y-intercept: 1/Vmax
LB plot for competitive inhibition
Vmax stays the same, Km increases.
LB plot for non-competitive inhibition
Vmax decreases, Km stays the same.
