Enzyme Kinetics and Inhibition Types Quiz

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Questions and Answers

What effect does a mixed inhibition have on Vmax and Km?

Vmax and Km both decrease

Vmax decreases, Km remains relatively unchanged (correct)

Vmax and Km both increase

Vmax increases, Km decreases

In irreversible inhibition, how do nerve gases and toxins typically impact enzymes?

Change Km or Vmax (correct)

Decrease Vmax only

Increase Km only

Leave Km and Vmax unaffected

In the Lineweaver–Burk double reciprocal plot, where do the lines intersect for mixed inhibition?

Near the y-axis, to the right of the x-axis

At the origin (0,0)

Near the x-axis, to the left of the y-axis (correct)

Near the x-axis, to the right of the y-axis

What type of inhibition does not compete with the substrate for the active site?

Uncompetitive Signup and view all the answers

How is allosteric control defined in enzyme regulation?

Binding of a molecule at one site affecting another site on the enzyme Signup and view all the answers

Which mechanism-based inhibitor falls into the irreversible inhibitors category?

Suicide inhibitors Signup and view all the answers

In the context of enzyme kinetics, what happens when a reversible inhibitor binds to an enzyme?

The inhibitor can 'equilibrate off,' leaving the original enzyme intact. Signup and view all the answers

Which type of reversible inhibitor reacts with the enzyme to form a covalent bond, rendering the protein inactive?

Irreversible inhibitor Signup and view all the answers

How do competitive inhibitors affect the Michaelis-Menten kinetics compared to uninhibited reactions?

Vmax remains unchanged Signup and view all the answers

Which statement is true regarding the Lineweaver–Burk plot for competitive inhibition?

Lines intersect at the x-axis Signup and view all the answers

What is the dissociation constant (KI) used to measure in relation to inhibitors?

Dissociation of the enzyme-inhibitor complex Signup and view all the answers

How does an irreversible inhibitor differ from a reversible inhibitor in terms of enzyme action?

Reversible inhibitors permanently inactivate enzymes. Signup and view all the answers

In noncompetitive inhibition, where does the inhibitor bind in relation to the enzyme's active site?

At a site distinct from the active site Signup and view all the answers

What happens to the KM value in noncompetitive inhibition?

It remains the same Signup and view all the answers

Which type of inhibition involves binding to an enzyme-substrate complex?

Uncompetitive inhibition Signup and view all the answers

What is the effect of increasing substrate concentration in noncompetitive inhibition?

Cannot overcome inhibition Signup and view all the answers

Which plot is commonly used to analyze enzyme kinetics and distinguish between types of inhibition?

Lineweaver–Burk plot Signup and view all the answers

How does noncompetitive inhibition affect Vmax in enzyme kinetics?

Vmax decreases Signup and view all the answers

Which type of inhibition involves altering the enzyme's structure around the active site?

Noncompetitive inhibition Signup and view all the answers

In which type of inhibition does increasing substrate concentration reduce inhibitor binding?

Competitive inhibition Signup and view all the answers

What happens to the slope of a Lineweaver–Burk plot when an inhibitor is present?

The slope decreases Signup and view all the answers

Study Notes

Enzyme Inhibition

Mixed inhibition: affects both Vmax and Km.
Irreversible inhibition: nerve gases and toxins typically bind covalently to the enzyme, rendering it inactive.

Lineweaver-Burk Plot

Mixed inhibition: lines intersect at a point other than the y-axis.
Competitive inhibition: lines intersect at the same point on the y-axis.
The Lineweaver-Burk plot is used to analyze enzyme kinetics and distinguish between types of inhibition.

Types of Inhibition

Non-competitive inhibition: does not compete with the substrate for the active site, binds to an allosteric site, and alters the enzyme's structure.
Allosteric control: regulation of enzyme activity by binding of molecules to sites other than the active site.
Uncompetitive inhibition: involves binding to an enzyme-substrate complex.
Reversible inhibition: inhibitor binds to the enzyme, reducing its activity, but can be removed, restoring enzyme activity.
Irreversible inhibition: inhibitor binds covalently to the enzyme, rendering it inactive.

Enzyme Kinetics

Competitive inhibition: increases Km, but Vmax remains unchanged.
Non-competitive inhibition: Km remains unchanged, but Vmax decreases.
Increasing substrate concentration in non-competitive inhibition: has no effect on inhibitor binding.
Increasing substrate concentration in competitive inhibition: reduces inhibitor binding.

Inhibitors

Dissociation constant (KI): measures the binding affinity of an inhibitor to an enzyme.
Mechanism-based inhibitor: falls into the irreversible inhibitors category, forms a covalent bond with the enzyme, rendering it inactive.
Covalent inhibitor: reacts with the enzyme to form a covalent bond, rendering the protein inactive.

Enzyme Regulation

Allosteric control: defined as the regulation of enzyme activity by binding of molecules to sites other than the active site.

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Description

Test your knowledge on enzyme kinetics, mixed inhibition, and irreversible inhibition. Understand the effects of changes in Vmax and Km, as well as the characteristics and examples of irreversible inhibitors.