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Mechanism Of Action Of Enzymes MDCAT MCQs with Answers

Mechanism Of Action Of Enzymes MDCAT MCQs

Welcome to the Mechanism Of Action Of Enzymes MDCAT MCQs with Answers. In this post, we have shared Mechanism Of Action Of Enzymes Multiple Choice Questions and Answers for PMC MDCAT 2024. Each question in MDCAT Biology offers a chance to enhance your knowledge regarding Mechanism Of Action Of Enzymes MCQs in this MDCAT Online Test.

What is the role of an enzyme in a chemical reaction?
a) Increases the activation energy
b) Decreases the activation energy
c) Decreases the reaction rate
d) Is consumed during the reaction

Answer
b) Decreases the activation energy

The specific location where a substrate binds to an enzyme is called the:
a) Active site
b) Binding site
c) Allosteric site
d) Receptor site

Answer
a) Active site

The induced fit model of enzyme action suggests that:
a) The active site has a rigid structure
b) The enzyme changes shape to fit the substrate
c) The enzyme and substrate fit perfectly like a lock and key
d) The substrate changes shape to fit the enzyme

Answer
b) The enzyme changes shape to fit the substrate

Enzymes work by:
a) Providing energy to the reaction
b) Altering the equilibrium constant of a reaction
c) Lowering the activation energy of the reaction
d) Binding irreversibly to substrates

Answer
c) Lowering the activation energy of the reaction

Which of the following is not a feature of enzyme action?
a) High specificity
b) Formation of an enzyme-substrate complex
c) Permanent alteration of the enzyme
d) Reusability of the enzyme

Answer
c) Permanent alteration of the enzyme

The mechanism through which enzymes speed up reactions is by:
a) Increasing the energy required for the reaction
b) Forming new bonds in the product
c) Stabilizing the transition state
d) Altering the substrate permanently

Answer
c) Stabilizing the transition state

Enzymes catalyze reactions by:
a) Breaking down themselves
b) Forming stronger bonds with the product
c) Decreasing the energy needed for reactants to reach the transition state
d) Increasing the concentration of products

Answer
c) Decreasing the energy needed for reactants to reach the transition state

What happens to the enzyme after it catalyzes a reaction?
a) It becomes part of the product
b) It is consumed in the reaction
c) It is regenerated and can be reused
d) It is inactivated permanently

Answer
c) It is regenerated and can be reused

Which term refers to the temporary molecule formed when an enzyme binds to its substrate?
a) Enzyme-product complex
b) Enzyme-substrate complex
c) Transition state complex
d) Allosteric complex

Answer
b) Enzyme-substrate complex

Which of the following best describes the lock-and-key model of enzyme action?
a) The enzyme’s active site is rigid and fits the substrate exactly
b) The enzyme’s active site changes to fit the substrate
c) The substrate changes to fit into the enzyme
d) The enzyme does not interact with the substrate directly

Answer
a) The enzyme’s active site is rigid and fits the substrate exactly

The active site of an enzyme is:
a) A rigid, unchangeable site on the enzyme
b) A site that is highly specific to the substrate
c) Always located at the allosteric site
d) Independent of the substrate’s structure

Answer
b) A site that is highly specific to the substrate

Enzyme specificity is mainly due to:
a) The size of the enzyme
b) The shape of the active site
c) The enzyme’s concentration
d) The enzyme’s pH

Answer
b) The shape of the active site

Which of the following statements about enzymes is true?
a) Enzymes are used up during a reaction
b) Enzymes increase the rate of a reaction by changing the reaction equilibrium
c) Enzymes are highly specific for their substrates
d) Enzymes do not bind to substrates

Answer
c) Enzymes are highly specific for their substrates

Which of the following is the correct term for the energy required to start a chemical reaction?
a) Activation energy
b) Kinetic energy
c) Potential energy
d) Catalytic energy

Answer
a) Activation energy

An enzyme’s ability to function can be affected by:
a) Temperature and pH
b) Substrate concentration
c) Presence of inhibitors
d) All of the above

Answer
d) All of the above

What happens to enzyme activity when the temperature is raised beyond the enzyme’s optimum level?
a) Activity increases indefinitely
b) Activity decreases due to denaturation
c) Activity remains the same
d) Activity increases as long as substrate is available

Answer
b) Activity decreases due to denaturation

The enzyme-substrate complex is formed during which stage of catalysis?
a) Before the reaction starts
b) During the transition state
c) After the reaction is completed
d) During the rate-determining step

Answer
b) During the transition state

What is the function of a cofactor in enzyme catalysis?
a) It inhibits the enzyme
b) It binds to the active site, changing its shape
c) It enhances the enzyme’s ability to bind the substrate
d) It permanently alters the enzyme

Answer
c) It enhances the enzyme’s ability to bind the substrate

Allosteric regulation of enzyme activity occurs when:
a) A molecule binds to the enzyme at a site other than the active site
b) The substrate binds irreversibly
c) The enzyme is broken down
d) The substrate concentration is very high

Answer
a) A molecule binds to the enzyme at a site other than the active site

Which of the following statements is correct about enzyme-substrate interaction?
a) Enzymes form strong covalent bonds with substrates
b) Enzymes form temporary, weak bonds with substrates
c) Enzymes are consumed in the reaction
d) Enzymes alter the substrates permanently

Answer
b) Enzymes form temporary, weak bonds with substrates

Enzyme inhibition where the inhibitor competes with the substrate for the active site is known as:
a) Non-competitive inhibition
b) Allosteric inhibition
c) Competitive inhibition
d) Irreversible inhibition

Answer
c) Competitive inhibition

Which is true for the mechanism of competitive inhibition?
a) The inhibitor binds to the allosteric site
b) The inhibitor binds to the same active site as the substrate
c) The inhibitor binds irreversibly to the enzyme
d) The inhibitor decreases Vmax without affecting Km

Answer
b) The inhibitor binds to the same active site as the substrate

The catalytic activity of an enzyme depends on its:
a) Molecular weight
b) Shape and structure
c) Inhibitors
d) Affinity for water

Answer
b) Shape and structure

What happens to the reaction rate when an enzyme is saturated with substrate?
a) The reaction rate continues to increase
b) The reaction rate decreases
c) The reaction rate remains constant at maximum
d) The enzyme denatures

Answer
c) The reaction rate remains constant at maximum

An enzyme that changes shape after substrate binding exhibits:
a) Lock and key model
b) Competitive inhibition
c) Induced fit model
d) Non-competitive inhibition

Answer
c) Induced fit model

Enzymes lower the activation energy of a reaction by:
a) Providing additional energy
b) Binding to the substrate
c) Making the transition state more stable
d) Increasing the reactant concentration

Answer
c) Making the transition state more stable

Which of the following best describes the transition state in an enzyme-catalyzed reaction?
a) The highest-energy state of the reaction
b) The lowest-energy state of the reaction
c) The enzyme-substrate complex formation
d) The final product state

Answer
a) The highest-energy state of the reaction

What is the effect of an enzyme on the reaction equilibrium?
a) It shifts the equilibrium toward the products
b) It shifts the equilibrium toward the reactants
c) It speeds up both forward and reverse reactions but does not change the equilibrium
d) It decreases the amount of product formed

Answer
c) It speeds up both forward and reverse reactions but does not change the equilibrium

Enzyme-catalyzed reactions follow which type of kinetics?
a) Michaelis-Menten kinetics
b) Zero-order kinetics
c) First-order kinetics
d) Second-order kinetics

Answer
a) Michaelis-Menten kinetics

What is the role of a transition state in an enzyme-catalyzed reaction?
a) It has lower energy than the substrates
b) It has higher energy than both substrates and products
c) It is a permanent structure formed during the reaction
d) It is the final form of the product

Answer
b) It has higher energy than both substrates and products

A substrate binds to the active site of an enzyme through:
a) Covalent bonds
b) Weak interactions like hydrogen bonds
c) Permanent ionic bonds
d) Repulsive forces

Answer
b) Weak interactions like hydrogen bonds

An enzyme that catalyzes the addition of a phosphate group to a molecule is called a:
a) Hydrolase
b) Transferase
c) Kinase
d) Isomerase

Answer
c) Kinase

The energy barrier that must be overcome for a reaction to occur is called the:
a) Equilibrium energy
b) Free energy
c) Activation energy
d) Catalytic energy

Answer
c) Activation energy

What is the mechanism by which enzymes decrease the activation energy of a reaction?
a) By stabilizing the reactants
b) By stabilizing the products
c) By stabilizing the transition state
d) By stabilizing the final product

Answer
c) By stabilizing the transition state

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