Covalent Catalysis in Enzymes Quiz: Test Your Knowledge

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Questions and Answers

What type of catalysis involves the formation of a covalent intermediate between the enzyme and the substrate?

Lock & Key Model

Induced Fit Model

Hydrophobic interactions

Covalent catalysis (correct)

Which group in the active site of serine proteases forms a covalent bond with a carbonyl carbon of a peptide bond?

Hydroxyl group of serine (correct)

Carbonyl group of serine

Amino group of serine

R group of serine

What interactions are involved in Fischer's Lock & Key Model?

Hydrogen bonds (correct)

Van der Waals forces

Ionic interactions

Covalent bonds

Why does successful binding of enzyme and substrate require them to approach each other closely over a broad surface?

To maximize weak interactions Signup and view all the answers

What is the term used to describe enzymes composed wholly of protein?

Simple enzymes Signup and view all the answers

According to Koshland's Induced Fit Model, what structural aspect is affected by changes in pH and temperature?

Tertiary structure Signup and view all the answers

What is the protein component of a complex enzyme known as?

Apoenzyme Signup and view all the answers

What explains the remarkable specificity of most enzymes according to the text?

Complementarity in the configuration of substrate and enzyme Signup and view all the answers

Which term describes a non-covalent binding between an apoenzyme and a non-protein component?

Coenzyme Signup and view all the answers

Enzymes that require a metal in their composition, binding and retaining the metal atom(s) under all conditions with high affinity, are known as:

Metalloenzymes Signup and view all the answers

What type of models is commonly favored to describe enzyme-substrate interactions?

Induced fit model Signup and view all the answers

Which clinical symptoms generally arise from the malfunction of enzymes lacking sufficient cofactors derived from vitamins?

Main clinical symptoms of dietary vitamin insufficiency Signup and view all the answers

What does the proposed model suggest about the initial interaction between enzyme and substrate?

It is weak but rapidly induces conformational changes in the enzyme Signup and view all the answers

What is the primary role of Catalysis by Bond Strain in enzyme-substrate interactions?

To induce structural rearrangements producing strained substrate bonds Signup and view all the answers

How does Catalysis by Proximity and Orientation contribute to enzyme catalysis?

By orienting reactive groups and bringing them into proximity with each other Signup and view all the answers

Which mechanism of catalysis involves the use of glutamate as a general acid catalyst?

Catalysis Involving Proton Donors and Acceptors Signup and view all the answers

What happens after binding takes place in enzyme-substrate interactions?

One or more mechanisms of catalysis generate transition-state complexes and reaction products Signup and view all the answers

Why do induced structural rearrangements take place with the binding of substrate and enzyme?

To induce strain in the substrate bonds for easier attainment of the transition state Signup and view all the answers

What is the main role of enzymes in speeding up a chemical reaction?

Lowering the energy of the transition state Signup and view all the answers

Why is pepsin most active in the acidic pH of 1–2 in the stomach?

The low pH stabilizes its active conformation Signup and view all the answers

How does trypsin exhibit different activity levels in the small intestine compared to the stomach?

It requires a high pH to be active in the small intestine Signup and view all the answers

What effect do enzymes have on the activation energy of a chemical reaction?

Lower the activation energy Signup and view all the answers

How do enzymes reduce the reaction entropy change during a chemical reaction?

By bringing substrates together in the correct orientation Signup and view all the answers

In what way can enzymes accelerate a reaction by creating an alternative pathway?

By forming an intermediate ES complex Signup and view all the answers

In uncompetitive inhibition, the inhibitor binds to:

ES-complex Signup and view all the answers

What type of inhibition is characterized by the inhibitor binding to the enzyme but not at the active site?

Non-competitive inhibition Signup and view all the answers

Which type of inhibition demonstrates residual enzymatic activity in the EIS-complex?

Mixed inhibition Signup and view all the answers

What can be said about the Km and Vmax values in uncompetitive inhibition compared to competitive inhibition?

Km remains the same, Vmax changes Signup and view all the answers

What type of feedback mechanism involves an inhibitor slowing down or stopping the production of a substance when its levels are sufficient?

Negative feedback Signup and view all the answers

Which type of enzymes often have allosteric binding sites for regulatory substances?

Enzymes subject to non-competitive inhibition Signup and view all the answers

Study Notes

Enzyme Basics

Enzymes can be simple (composed only of protein) or complex (composed of protein and a small organic molecule, known as a coenzyme or prosthetic group)
Complex enzymes are also known as holoenzymes
The protein component of a complex enzyme is called the apoenzyme, while the non-protein component is called the coenzyme or prosthetic group

Enzyme-Substrate Interactions

The induced fit model is the favored model of enzyme-substrate interaction
In this model, the initial interaction between enzyme and substrate is relatively weak, but induces conformational changes in the enzyme that strengthen binding and bring catalytic sites close to substrate bonds to be altered
There are four possible mechanisms of catalysis:
- Catalysis by bond strain
- Catalysis by proximity and orientation
- Catalysis involving proton donors (acids) and acceptors (bases)
- Covalent catalysis

Enzyme Mechanisms

Enzymes can act in several ways to lower the energy of activation and speed up a chemical reaction:
- Lowering the activation energy by creating an environment in which the transition state is stabilized
- Lowering the energy of the transition state, but without distorting the substrate
- Providing an alternative pathway
- Reducing the reaction entropy change by bringing substrates together in the correct orientation to react

Enzyme Inhibition

Uncompetitive inhibition: the inhibitor can only bind to the ES-complex, forming an enzymatically inactive EIS-complex
Non-competitive inhibition: the inhibitor can bind to the enzyme at the same time as the substrate, but not to the active site
Mixed inhibition: the EIS-complex has residual enzymatic activity

Regulation of Enzymes

Inhibitors may act as part of a feedback mechanism to regulate enzyme activity
Enzymes subject to this form of regulation are often multimeric and have allosteric binding sites for regulatory substances
Their substrate/velocity plots are not hyperbolar, but sigmoidal (S-shaped)

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Description

Test your knowledge on covalent catalysis mechanisms in enzymes, where substrates form covalent intermediates with active sites. Explore examples like serine proteases involved in proteolysis. This quiz covers key concepts in enzyme catalysis.

Covalent Catalysis in Enzymes Quiz