36 Questions
What happens to reaction velocity as temperature increases?
Increases until a peak is reached, then decreases due to denaturation of proteins
What is the effect of substrate concentration on enzyme reaction velocity?
Increases until a maximal velocity (Vmax) is reached
What defines an irreversible inhibitor of enzyme activity?
Forms covalent bonds and permanently inactivates enzymes
How does noncompetitive inhibition affect enzyme activity?
Binds to an allosteric site, changing enzyme shape and reducing activity
What characteristic is reflected by the Michaelis-Menten constant (Km)?
Affinity of the enzyme for the substrate
In Michaelis-Menten kinetics, what does Km represent?
Substrate concentration at half the maximum reaction velocity
How does a low Km value affect an enzyme-substrate reaction?
It indicates high affinity between the enzyme and substrate
What happens to the reaction velocity when [S] < Km in Michaelis-Menten kinetics?
Velocity is nearly proportional to the substrate concentration
Which type of inhibition results in a change in Vmax but no change in Km?
Noncompetitive inhibition
How does pH affect enzyme activity?
Optimal pH increases enzyme activity
What does the Michaelis-Menten equation describe?
How reaction velocity varies with substrate concentration
What is the main assumption/condition for Michaelis-Menten kinetics?
The relative concentration of enzyme is much less than that of the substrate
In terms of enzyme kinetics, what does Vmax represent?
The maximum reaction velocity of an enzyme at high substrate concentrations
Which type of inhibition involves a substance binding to an enzyme at the active site, preventing the substrate from binding?
Competitive inhibition
How does pH affect enzyme activity?
Extreme pH levels can denature enzymes and affect their activity
What characterizes noncompetitive inhibition?
It decreases the efficiency of the enzyme by changing its shape
What happens to the velocity of a reaction when zero order of substrate concentration is greater than Km?
The velocity of the reaction is constant and equal to Vmax.
Why does increasing the substrate concentration not reverse the decrease in Vmax caused by a noncompetitive inhibitor?
The noncompetitive inhibitor binds to the allosteric site, affecting the ES complex
Which type of enzyme kinetics show a hyperbolic curve according to Michaelis-Menten?
Single-substrate kinetics like myoglobin binding to O2.
In competitive inhibition, how do the inhibitors affect enzyme activity?
They bind to the active site of the enzyme.
What type of curve do allosteric enzymes exhibit in terms of their kinetics?
Sigmoidal curve.
How do statin drugs act as competitive inhibitors in cholesterol biosynthesis?
They compete with the natural substrate of HMG-CoA reductase.
How do you determine Vmax in a Lineweaver-Burk plot?
By finding the y-intercept.
How do β-lactam antibiotics like penicillin act as enzyme inhibitors?
By inhibiting enzymes crucial for bacterial cell wall synthesis.
What is the purpose of plotting reciprocal 1/v0 and 1/[S] to obtain a straight line in enzyme kinetics?
To calculate Km and Vmax.
What effect does aspirin have on prostaglandin and thromboxane synthesis?
It irreversibly inhibits their synthesis.
In competitive inhibition, how does the presence of an inhibitor affect the Km value?
Km increases.
What is the main difference between competitive and noncompetitive inhibitors?
Competitive inhibitors compete with the substrate for the active site, while noncompetitive inhibitors bind at a different site.
In competitive inhibition, how does the presence of an inhibitor affect the Lineweaver-Burk plot?
1/Vmax remains unchanged while 1/Km increases.
How does a noncompetitive inhibitor affect enzyme activity?
It binds at a site different from the substrate, altering enzyme conformation.
Which statement is true about competitive inhibition?
Increasing substrate concentration can overcome competitive inhibition effects.
What effect does a competitive inhibitor have on Km for a given substrate?
Km increases, requiring more substrate to reach Vmax.
How is enzyme activity affected by noncompetitive inhibition?
[S] needed to reach Vmax increases due to decreased enzyme efficiency.
What is the primary effect of a noncompetitive inhibitor on enzyme function?
[S] needed for Vmax increases due to altered enzyme conformation.
Which of the following statements accurately describes competitive inhibition?
[S] required for Vmax decreases due to elevated Km values.
What distinguishes noncompetitive inhibition from competitive inhibition?
[S] required for Vmax is unaffected by competitive inhibition but not by noncompetitive inhibition.
Explore how enzymes function in living cells through in vitro studies. Learn about the impact of substrate concentration on enzyme-catalyzed reactions, including the concept of Vmax and saturation. Discover the influence of temperature and pH on enzyme activity.
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