Enzyme Regulation: Inhibition Overview

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Questions and Answers

What role do inhibitors play in enzyme activity?

They enhance the reaction rate.

They prevent the enzyme from catalyzing reactions. (correct)

They increase substrate availability.

They permanently alter the enzyme structure.

What is the primary difference between competitive and non-competitive inhibition?

Non-competitive inhibitors bind to the substrate, while competitive inhibitors do not.

Competitive inhibitors can enhance enzyme activity.

Competitive inhibitors bind to the active site, while non-competitive inhibitors do not. (correct)

Only non-competitive inhibitors can be reversible.

What happens to the reaction rate as the concentration of a competitive inhibitor increases?

The reaction rate increases significantly.

The reaction rate remains the same regardless of inhibitor concentration.

The reaction rate fluctuates randomly.

The reaction rate decreases until it stops completely. (correct)

How does non-competitive inhibition affect enzyme functionality?

It decreases substrate binding efficiency. Signup and view all the answers

Which of the following statements about reversible inhibitors is true?

They bind weakly and can be released. Signup and view all the answers

What is the effect of a non-competitive inhibitor on the saturation curve of an enzyme?

It decreases the maximum reaction rate achievable. Signup and view all the answers

What can be a necessary role of inhibitors in the human body?

To regulate metabolic pathways. Signup and view all the answers

Which characteristic of irreversible inhibition is true?

The binding is usually covalent and permanent. Signup and view all the answers

What occurs when an irreversible inhibitor binds to an enzyme?

It completely disables the enzyme. Signup and view all the answers

What is the role of an allosteric activator?

It stabilizes the conformation with a functional active site. Signup and view all the answers

How does feedback inhibition impact enzymatic reactions in a metabolic pathway?

It slows or stops the reaction when excess product accumulates. Signup and view all the answers

Where is the allosteric site located on an enzyme?

In a specific region that is not the active site. Signup and view all the answers

What happens to threonine deaminase when isoleucine accumulates?

The enzyme is converted to a low-affinity state. Signup and view all the answers

What is the classification of a regulator that stabilizes the conformation lacking an active site?

Allosteric inhibitor Signup and view all the answers

Which statement accurately describes the oscillation of allosteric enzymes?

They naturally oscillate between active and inactive forms. Signup and view all the answers

What signifies a product's role in feedback inhibition of a metabolic pathway?

It inhibits the first enzyme of the pathway when in excess. Signup and view all the answers

Study Notes

Enzyme Regulation: Inhibition

Inhibitors: Molecules that bind to an enzyme, preventing it from catalyzing reactions. They can block substrate access, slowing or stopping the reaction.
Irreversible Inhibition: Occurs when the inhibitor forms covalent bonds with the enzyme, permanently disabling it.
Reversible Inhibition: Occurs when the inhibitor's binding is weak and easily reversed. Common in metabolic regulation.
Competitive Inhibition: The inhibitor binds to the same active site as the substrate. High inhibitor concentration stops the reaction completely as inhibitor and substrate compete.

Competitive Inhibition & Saturation Curves

Competitive inhibitors alter the apparent Km (Michaelis constant) of the enzyme.
By increasing the inhibitor concentration, the enzyme's affinity for substrate is reduced and the saturation curve shifts to the right, implying a greater substrate concentration is needed for the same reaction rate. Effectively higher Km.

Non-Competitive Inhibition & Saturation Curves

Non-competitive inhibition: Inhibitors bind to a site other than the active site (allosteric site), changing the enzyme's shape and reducing its ability to bind the substrate.
Non-competitive inhibitors alter the Vmax of the enzyme.
Increasing the inhibitor concentration decreases the reaction rate (lower Vmax) regardless of substrate concentration.
- The saturation curve stays similar in shape just shifts down because the the maximum rate of the reaction is lowered.

Overcoming Competitive Inhibition

Increasing substrate concentration can outcompete the inhibitor for the active site, restoring enzyme activity.

Importance of Inhibitors

Inhibitors play a crucial regulatory role in metabolism, regulating the rates of biochemical pathways.

Reversible vs Irreversible Inhibition

Reversible inhibition involves weak binding, allowing the inhibitor to detach and enzyme function to return.
Irreversible inhibition involves strong covalent bonding, permanently disabling the target enzyme.

Allosteric Control on Enzyme Activity

Allosteric Enzymes: Enzymes that have an allosteric site in addition to the active site. This site can be between subunits.
Allosteric Site: A specific site on the enzyme (not the active site) where molecules (effectors) can bind.
Allosteric sites have two conformations (active and inactive) that are in dynamic equilibrium.
- Binding to an allosteric site can stabilize either the active or inactive conformation.
Effectors: Molecules (activators or inhibitors) that bind to allosteric sites, regulating enzyme activity.

Feedback Inhibition (Negative Feedback)

Feedback Inhibition: End-product(s) in a metabolic pathway regulate the first step of the pathway via an allosteric effect.
High product levels act as an inhibitor, slowing further reaction rates.
Low product level inhibits reduces the inhibition, increasing the rate.
Feedback inhibition is a form of regulation within pathways preventing unnecessary synthesis of materials, ensuring resources are efficiently used.

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Description

This quiz explores key concepts of enzyme inhibition including irreversible and reversible inhibition, competitive inhibition, and saturation curves. Understand how inhibitors work and their effects on the enzyme's substrate affinity as illustrated in saturation curves.