Enzyme Regulation and Feedback Control

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Questions and Answers

Why is it necessary for living systems to regulate enzyme activity?

To decrease metabolic processes

To slow down growth

To increase enzyme production

To coordinate metabolic processes and adapt to environmental changes (correct)

What happens when an enzyme continues to catalyze a reaction that produces a product present in plentiful amounts in a cell?

The reaction is accelerated

Energy is conserved

Energy is wasted (correct)

The enzyme is activated

What type of inhibition is associated with controlling the availability of an enzyme?

Irreversible inhibition

Competitive inhibition

Noncompetitive inhibition (correct)

Uncompetitive inhibition

What is the result of covalent modifications to an enzyme's conformation or structure?

Irreversible inhibition Signup and view all the answers

Why is it necessary to 'turn off' an enzyme when its substrate concentration is very low?

To conserve energy Signup and view all the answers

What is the purpose of regulating enzyme activity in a cell?

To coordinate metabolic processes and promote adaptations Signup and view all the answers

What is the primary function of allosteric enzymes?

To regulate enzyme activity through feedback control Signup and view all the answers

What is the result of a negative allosteric effector binding to an enzyme?

Decreased enzyme activity Signup and view all the answers

What type of inhibition occurs when an inhibitor forms a strong covalent bond with the enzyme?

Irreversible inhibition Signup and view all the answers

What is the purpose of feedback control in enzyme regulation?

To shut down an entire reaction sequence Signup and view all the answers

What is the effect of an irreversible inhibitor on an enzyme?

Permanently deactivates the enzyme Signup and view all the answers

What is the role of zymogens in regulating enzyme activity?

To produce enzymes in an inactive form Signup and view all the answers

What is the primary mechanism by which an enzyme recognizes its specific substrate?

Geometric shape and conformational complementarity Signup and view all the answers

What is the advantage of the induced fit model over the lock-and-key model?

It allows for more flexibility in the active site Signup and view all the answers

Which of the following forces is responsible for drawing the substrate into the active site of an enzyme?

Hydrogen bonding and hydrophobic interactions Signup and view all the answers

What is the term for the ability of an enzyme to choose an exact substrate from a group of similar chemical molecules?

Specificity Signup and view all the answers

What is the consequence of an enzyme having a geometric specificity?

It can act on multiple substrates with similar molecular geometry Signup and view all the answers

Which enzyme can oxidize both ethanol and methanol to yield corresponding aldehydes?

Alcohol dehydrogenase Signup and view all the answers

Study Notes

Importance of Enzyme Regulation

Living systems must regulate enzymatic catalytic activity to coordinate metabolic processes, adapt to environmental changes, and ensure proper growth and life cycles.

Mechanisms of Enzyme Regulation

Control of enzyme availability through production of zymogens
Control of enzymatic activity through covalent modifications of conformation or structure (irreversible inhibition)
Feedback control associated with allosteric enzymes (noncompetitive inhibition)

Feedback Control

Allosteric enzymes have two receptor sites: one for the substrate and one for an inhibitor or activator molecule
Positive allosteric effectors increase enzyme activity, while negative allosteric effectors decrease it
Feedback control involves the inhibition of the first enzyme in a pathway by the product of the reaction sequence
This process shuts down the entire sequence when the end product accumulates

Irreversible Inhibition

Irreversible inhibitors bind tightly or form strong covalent bonds with functional groups in the active site, permanently deactivating the enzyme
Irreversible inhibition destroys the active site, decreasing the reaction rate

Applications of Inhibitors

Negative feedback: end-point or end-product inhibition
Medicine: antibiotics, sulphonamides, sedatives, and stimulants
Poisons: snake bites, plant alkaloids, and nerve gases

Zymogens and Regulation

Zymogens are inactive enzymes produced by cells, which can be activated as needed
The active site of an enzyme has a fixed, rigid geometrical conformation complementary to the substrate

Enzyme Specificity

Specificity is the ability of an enzyme to choose the exact substrate from a group of similar molecules
Specificity operates through structural and conformational complementarity between enzymes and substrates
Geometric specificity: a single enzyme can act on different substrates with similar molecular geometry, reducing specificity

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Description

This quiz covers the regulation of enzyme activity, including the role of allosteric enzymes, positive and negative allosteric effectors, and feedback control mechanisms.