Chapter 12 Flashcards
What is reaction velocity (v)?
Rate of change from reactants to products with respect to time
What is the rate constant (k)?
Describes how a reaction is dependent on the concentration of reactant/substrate
What is the equation for reaction velocity (v)?
v = k[A]
What do the enzyme and substrate react to form?
Michaelis (ES) Complex
What are the three assumptions of enzyme kinetics?
Initial Velocity Assumption
Equilibrium Assumption
Steady State Assumption
What does the initial velocity assumption say?
Before a build-up of P then the reverse reaction is negligible (ignore P + E -> ES)
What does the equilibrium assumption say?
The first step of the reaction reaches equilibrium before the production of products
What is the equation for the dissociation constant (Ks)?
Ks = [E][S] / [ES]
What does the steady state assumption say?
The rate of ES formation equals the rate of ES consumption ([ES] = constant)
What is the Michaelis-Menten equation?
Vo = Vmax[S] / Km + [S]
What is Vmax?
The theoretical maximum rate; would require that all enzyme molecules be bound to the substrate
What is Km?
Substrate concentration that reaches half maximum velocity
What does a small Km mean?
The substrate has a high affinity for the enzyme
What does a large Km mean?
The substrate has a low affinity for the enzyme
What is the equation for Km?
k-1 + k2 / k1
What is Kcat?
Turnover number; number of substrate molecules converted to product per enzyme molecule per unit of time
What is the equation for Kcat?
Vmax / [E]t
What is the formula for catalytic efficiency?
Vo = (Kcat/Km) [E][S]
What is maximum catalytic efficiency?
10^9 m^-1 s^-1
What limits catalytic efficiency?
Diffusion limit
What is the diffusion limit?
How quickly the ES complex will get together
What is the purpose of a lineweaver-burk plot?
Plot Michaelis-Menten on a linear plot
What are the three types of enzyme inhibition?
Competitive
Uncompetitive
Non-competitive
What is competitive inhibition?
Inhibitor competes with substrate for binding site
What does the Lineweaver-Burk graph look like for competitive inhibition?
Same y-intercept, different slopes
What is uncompetitive inhibition?
Inhibitor binds to ES complex
What does the Lineweaver-Burk graph look like for uncompetitive inhibition?
Same slopes, different y-intercepts
What is noncompetitive inhibition?
Combination of competitive and uncompetitive inhibition; inhibitor binds at an exosite whether or not substrate is bound
For mixed inhibition what does it mean is Ki = Ki`?
Equal affinity
For mixed inhibition what does it mean is Ki < Ki`?
More affinity for the enzyme
For mixed inhibition what does it mean is Ki > Ki`?
More affinity for ES complex
What is an ordered single-displacement reaction?
Bimolecular reaction in which the leading substrate must bind first followed by an ordered release of product
What is a random single-displacement reaction?
Bimolecular reaction in which either substrate may bind first
What is a double displacement reaction?
Ping-pong reaction
Bimolecular reaction in which the product of the first reaction is released prior to reaction with second substrate
