24 Questions
What is the relationship between the initial velocity Vo and the substrate concentration [S] in enzyme catalysis?
Vo is directly proportional to [S]
What is the role of the enzyme in the Michaelis-Menten equation?
To bind to the substrate and form an enzyme-substrate complex
What is the significance of the Michaelis-Menten constant KM?
It is the concentration of the substrate at which the enzyme is half-saturated
What is the assumption of the Michaelis-Menten equation?
The substrate concentration [S] is much greater than the enzyme concentration [E]
What is the relationship between the maximum velocity Vmax and the initial velocity Vo?
Vmax is equal to Vo
What is the purpose of the formation of the enzyme-substrate complex in enzyme catalysis?
To facilitate the binding of the substrate to the enzyme
What is the rate-determining step in enzyme catalysis?
The formation of the transition state
What is the effect of increasing the substrate concentration [S] on the initial velocity Vo?
Vo increases initially and then levels off
What is the study of the rates at which chemical reactions occur?
Kinetics
What is the equation for the rate of a reaction with aA + bB → P?
Rate = k[A]a[B]b
What is the order of a reaction with rate equation Rate = k[A]a[B]b?
a + b
What is the rate equation for a first-order reaction A → P?
v = -d[A]/dt = k[A]
What is the term for the time it takes for the concentration of a reactant to decrease to half of its initial value?
Half-life
What is the rate equation for a second-order reaction A + B → P?
v = k[A][B]
What is the term for the state in which the reactants and products are in equilibrium?
Equilibrium
What is the effect of catalysis on the free energy of activation?
Decreases the free energy of activation
What is the effect of increasing [S] on the Vo in the Michaelis-Menten equation?
Vo increases and approaches Vmax
What is the purpose of the Lineweaver-Burk plot?
To determine the KM value
In competitive inhibition, what is the effect of increasing [I] on the Vo?
Vo decreases
What is the equation for the Eadie-Hofstee plot?
Vo = -KM/[S] + Vmax
What is the difference between competitive and non-competitive inhibition?
Competitive inhibition affects KM, while non-competitive inhibition affects Vmax
What is the purpose of the Michaelis-Menten equation?
To describe the kinetics of enzyme-catalyzed reactions
What is the effect of increasing [S] on the Vo at low [S] values?
Vo increases rapidly
What is the Km value in the Michaelis-Menten equation?
The substrate concentration at which Vo is half of Vmax
Study Notes
First-Order Reaction
- V = kF[S] – kB[P]
- kF[S] = kB[P] at equilibrium
- Vo = kF[S]
- Initial velocity (Vo) is proportional to substrate concentration [S]
Enzyme Catalysis
- Formation of enzyme-substrate complex: E + S → E—S
- Binding: k1, k-1; Catalysis: k2
- Vo = k2[ES]
Michaelis-Menten Formulation
- Formation of enzyme-substrate complex: E + S → E—S
- Transition state: E—S* → E + P
- Michaelis-Menten equation: Vo = k+2[E]A[S] / (KM + [S])
- [EA] = total active enzyme molecules
- Vmax = k2[E]A
Enzyme Kinetics
- Progress curves: steady-state
- Lineweaver-Burk plot: 1/Vo = 1/Vmax + KM/Vmax[1/[S]]
- Eadie-Hofstee plot: Vo = -KM/Vmax[1/[S]] + Vmax
Inhibition
- Competitive inhibitor: E + I → E—I (inactive)
- Non-competitive inhibitor: E + S → E—S; E—I (inactive)
- Competitive inhibitor plots: 1/Vo = 1/Vmax + KI/Vmax[1/[S]]
- Non-competitive inhibitor plots: Vo = -KM/Vmax[1/[S]] + Vmax
Chemical Kinetics
- Definition: study of rates of chemical reactions
- Elementary reactions: A → P
- Rate equations: Rate = k[A]a[B]b (a + b = order of reaction)
- Molecularity of reaction: first-order, second-order, etc.
Rate Equations
- First-order reaction: v = -d[A]/dt = k[A]
- Second-order reaction: v = -d[A]/dt = k[A][B]
Transition State
- Definition: high-energy state during chemical reaction
- Example: CH3Br + OH- → CH3OH + Br-
Thermodynamics of the Transition State
- Two-step reactions: k1, k2
- Rate-determining step: the slowest step determines the overall rate
Accelerating Chemical Reactions
- Heat: increases kinetic energy of molecules
- pH: affects reaction rates
- Catalysis: reduces ∆G‡, increasing reaction rates
This quiz covers the concepts of first-order reaction, enzyme catalysis, and the Michaelis-Menten formulation. It includes the kinetics of substrate-enzyme interactions and the calculation of initial velocity.
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