Podcast
Questions and Answers
What type of catalysis involves the formation of a covalent intermediate between the enzyme and the substrate?
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?
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?
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?
Why does successful binding of enzyme and substrate require them to approach each other closely over a broad surface?
What is the term used to describe enzymes composed wholly of protein?
What is the term used to describe enzymes composed wholly of protein?
According to Koshland's Induced Fit Model, what structural aspect is affected by changes in pH and temperature?
According to Koshland's Induced Fit Model, what structural aspect is affected by changes in pH and temperature?
What is the protein component of a complex enzyme known as?
What is the protein component of a complex enzyme known as?
What explains the remarkable specificity of most enzymes according to the text?
What explains the remarkable specificity of most enzymes according to the text?
Which term describes a non-covalent binding between an apoenzyme and a non-protein component?
Which term describes a non-covalent binding between an apoenzyme and a non-protein component?
Enzymes that require a metal in their composition, binding and retaining the metal atom(s) under all conditions with high affinity, are known as:
Enzymes that require a metal in their composition, binding and retaining the metal atom(s) under all conditions with high affinity, are known as:
What type of models is commonly favored to describe enzyme-substrate interactions?
What type of models is commonly favored to describe enzyme-substrate interactions?
Which clinical symptoms generally arise from the malfunction of enzymes lacking sufficient cofactors derived from vitamins?
Which clinical symptoms generally arise from the malfunction of enzymes lacking sufficient cofactors derived from vitamins?
What does the proposed model suggest about the initial interaction between enzyme and substrate?
What does the proposed model suggest about the initial interaction between enzyme and substrate?
What is the primary role of Catalysis by Bond Strain in enzyme-substrate interactions?
What is the primary role of Catalysis by Bond Strain in enzyme-substrate interactions?
How does Catalysis by Proximity and Orientation contribute to enzyme catalysis?
How does Catalysis by Proximity and Orientation contribute to enzyme catalysis?
Which mechanism of catalysis involves the use of glutamate as a general acid catalyst?
Which mechanism of catalysis involves the use of glutamate as a general acid catalyst?
What happens after binding takes place in enzyme-substrate interactions?
What happens after binding takes place in enzyme-substrate interactions?
Why do induced structural rearrangements take place with the binding of substrate and enzyme?
Why do induced structural rearrangements take place with the binding of substrate and enzyme?
What is the main role of enzymes in speeding up a chemical reaction?
What is the main role of enzymes in speeding up a chemical reaction?
Why is pepsin most active in the acidic pH of 1–2 in the stomach?
Why is pepsin most active in the acidic pH of 1–2 in the stomach?
How does trypsin exhibit different activity levels in the small intestine compared to the stomach?
How does trypsin exhibit different activity levels in the small intestine compared to the stomach?
What effect do enzymes have on the activation energy of a chemical reaction?
What effect do enzymes have on the activation energy of a chemical reaction?
How do enzymes reduce the reaction entropy change during a chemical reaction?
How do enzymes reduce the reaction entropy change during a chemical reaction?
In what way can enzymes accelerate a reaction by creating an alternative pathway?
In what way can enzymes accelerate a reaction by creating an alternative pathway?
In uncompetitive inhibition, the inhibitor binds to:
In uncompetitive inhibition, the inhibitor binds to:
What type of inhibition is characterized by the inhibitor binding to the enzyme but not at the active site?
What type of inhibition is characterized by the inhibitor binding to the enzyme but not at the active site?
Which type of inhibition demonstrates residual enzymatic activity in the EIS-complex?
Which type of inhibition demonstrates residual enzymatic activity in the EIS-complex?
What can be said about the Km and Vmax values in uncompetitive inhibition compared to competitive inhibition?
What can be said about the Km and Vmax values in uncompetitive inhibition compared to competitive inhibition?
What type of feedback mechanism involves an inhibitor slowing down or stopping the production of a substance when its levels are sufficient?
What type of feedback mechanism involves an inhibitor slowing down or stopping the production of a substance when its levels are sufficient?
Which type of enzymes often have allosteric binding sites for regulatory substances?
Which type of enzymes often have allosteric binding sites for regulatory substances?
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.
