Biochemistry: Enzyme Action Mechanism
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Questions and Answers

What is one way that enzymes accelerate chemical reactions?

  • By bringing substrates into close proximity (correct)
  • By increasing the concentration of substrates
  • By inhibiting the reverse reaction
  • By reducing the temperature of the reaction

What happens to the enzyme after a reaction is completed?

  • It cannot bind to another substrate
  • It gets consumed along with the substrate
  • It changes permanently
  • It remains unchanged (correct)

In what way does the induced fit model relate to enzyme activity?

  • It results in a conformational change in the enzyme (correct)
  • It allows the substrate to bind without any changes
  • It inhibits substrate binding
  • It maintains the enzyme's original shape

At equilibrium during an enzyme-catalyzed reaction, what is true about the forward and reverse reactions?

<p>Both reactions occur at equal rates (C)</p> Signup and view all the answers

Which mechanism describes how the binding of the substrate affects the enzyme's shape?

<p>Strain and Distortion Mechanism (A)</p> Signup and view all the answers

What is a consequence of the high concentration of product in an enzyme reaction mixture?

<p>It can potentially halt the forward reaction (B)</p> Signup and view all the answers

Why is it stated that enzyme-catalyzed reactions are theoretically reversible?

<p>Because reactions can proceed both ways at equilibrium (C)</p> Signup and view all the answers

What role does the catalytic group play in enzyme function?

<p>It facilitates the breakdown of the substrate's bonds (C)</p> Signup and view all the answers

What is the primary role of enzymes in biochemical reactions?

<p>To accelerate the rate of reactions by lowering activation energy (B)</p> Signup and view all the answers

Which statement accurately describes the transition state in enzyme reactions?

<p>It is a temporary and unstable state of the enzyme-substrate complex. (A)</p> Signup and view all the answers

What type of catalysis involves the active site of an enzyme acting as a proton donor?

<p>General acid-base catalysis (C)</p> Signup and view all the answers

Why do some enzymes form unstable enzyme-substrate complexes?

<p>To allow for further reactions to produce final products (C)</p> Signup and view all the answers

What defines the activation energy in enzymatic reactions?

<p>The energy required to initiate the transition state (B)</p> Signup and view all the answers

Which of the following best describes covalent catalysis?

<p>Enzymes form temporary covalent bonds with substrates to assist reactions. (A)</p> Signup and view all the answers

How does the free energy of activation relate to catalysis?

<p>Enzymes lower the free energy of activation, increasing reaction rates. (A)</p> Signup and view all the answers

What is one effect of enzyme catalysis in reactions?

<p>It allows for the reaction to occur at lower temperatures. (B)</p> Signup and view all the answers

What is the role of a catalyst in a chemical reaction?

<p>To lower the energy of activation for the reaction (C)</p> Signup and view all the answers

What happens to the enzyme after a product is formed?

<p>It is free to combine with another substrate molecule (D)</p> Signup and view all the answers

Which statement about the energy of activation is correct?

<p>It is the energy needed to reach the transition state (A)</p> Signup and view all the answers

How does the presence of an enzyme affect the reaction's overall free energy change?

<p>It does not alter the overall free energy change (C)</p> Signup and view all the answers

What is the transient state formed when a substrate combines with a catalyst called?

<p>Activated complex (C)</p> Signup and view all the answers

What must the substrate possess for a reaction to occur?

<p>Sufficient energy to reach the transition state (C)</p> Signup and view all the answers

In the context of enzyme-catalyzed reactions, what is meant by 'transition state'?

<p>The point at which the chemical bonds are breaking and forming (A)</p> Signup and view all the answers

What does the energy required to bring all molecules in one gram mole to a given state represent?

<p>Free energy of activation (A)</p> Signup and view all the answers

What is formed when an enzyme binds with a substrate?

<p>Enzyme-substrate complex (A)</p> Signup and view all the answers

Which component of an enzyme specifically binds to the substrate during the catalytic process?

<p>Catalytic site (B), Binding site (D)</p> Signup and view all the answers

What type of interaction primarily stabilizes the enzyme-substrate complex?

<p>Hydrogen bonds (C)</p> Signup and view all the answers

In terms of size comparison, how do enzymes relate to their substrates?

<p>Enzymes are much larger than substrates. (A)</p> Signup and view all the answers

What is the purpose of the active site of an enzyme?

<p>To bind the substrate and catalyze reactions (D)</p> Signup and view all the answers

Which feature distinguishes the active center of an enzyme?

<p>It contains specific sites that bind substrates. (A)</p> Signup and view all the answers

What is the role of transitional (intermediate) compounds in enzyme activity?

<p>They are formed during the catalytic process. (D)</p> Signup and view all the answers

Which type of amino acid group is important for the active sites of enzymes?

<p>Amino acids with sulfhydryl groups (A)</p> Signup and view all the answers

What is the primary role of the enzyme-substrate complex?

<p>To transform the substrate into a product. (A)</p> Signup and view all the answers

Which statement accurately describes the enzyme's function after the substrate is transformed?

<p>The enzyme returns to its original form. (C)</p> Signup and view all the answers

What key interaction is compared to the relationship between an enzyme and its substrate?

<p>A lock and key. (A)</p> Signup and view all the answers

According to the Michaelis-Menten theory, what is formed when an enzyme combines with its substrate?

<p>Enzyme-substrate complex. (A)</p> Signup and view all the answers

Which amino acids are mentioned as present at the active site of enzymes?

<p>Tyrosine and lysine. (A)</p> Signup and view all the answers

What is the immediate product of the reaction catalyzed by the enzyme after the enzyme-substrate complex is formed?

<p>Product. (D)</p> Signup and view all the answers

In enzyme kinetics, what does the term 'active site' refer to?

<p>The specific region of the enzyme where substrate binding occurs. (B)</p> Signup and view all the answers

What describes the process of the enzyme returning to its original state after catalyzing a reaction?

<p>Enzyme regeneration. (D)</p> Signup and view all the answers

Flashcards

Active Site

The specific region on an enzyme where the substrate binds.

Enzyme-Substrate Complex

A temporary complex formed when an enzyme binds to its substrate.

Michaelis-Menten Theory

The model that explains how enzymes work by binding to their substrates, forming an enzyme-substrate complex.

Substrate

The molecule that an enzyme acts upon, changing it into a product.

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Product

The molecule produced by an enzyme from the substrate.

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Michaelis Constant (Km)

A measure of how well an enzyme binds to its substrate. It represents the substrate concentration needed to reach half-maximal velocity.

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Vmax

The maximum rate at which an enzyme can catalyze a reaction.

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Active Site Amino Acids

Amino acids that are commonly found in the active site of an enzyme.

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Enzyme-Substrate Complex (ES)

The temporary complex formed between an enzyme and its substrate during a reaction.

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Catalytic Site

The part of the active site responsible for chemically transforming the substrate into product.

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Enzyme Catalysis

The process by which an enzyme lowers the activation energy of a reaction, speeding it up.

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Specificity of Enzyme Action

The binding between an enzyme and its substrate is highly specific, meaning only certain substrates can fit into the active site.

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Binding Interactions

Weak chemical interactions, like hydrogen bonds and Van der Waals forces, that hold the substrate in the active site.

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Transitional (Intermediate) Compound

The temporary, unstable intermediate formed during a reaction, where the substrate is in the process of being converted to the product.

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Stabilizing Forces

Forces that stabilize the interaction between an enzyme and its substrate, ensuring they stay together long enough for the reaction to occur.

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Enzyme Reusability

Enzymes don't get used up in reactions; they can bind to and process many substrate molecules.

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Enzyme Reaction Reversibility

Reactions are theoretically reversible, but the forward reaction is favored when the product concentration is low.

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Enzyme Acceleration

Enzymes significantly speed up chemical reactions.

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Proximity and Orientation

Enzymes bring the substrate and catalytic groups close together, making the chemical reaction more likely.

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Strain and Distortion

When a substrate binds to an enzyme, the enzyme's shape changes, making the substrate less stable and more likely to react.

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Induced Fit Model

The process where an enzyme changes the shape of a substrate, aiding in its conversion to a product.

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Activation Energy

Energy required for molecules to reach a 'transition state' where they are likely to react and form a product.

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Transition State

A special state where molecules have enough energy to react and easily transform into a product.

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Catalyst

A substance that speeds up a chemical reaction without being consumed in the process.

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Enzyme

A biological catalyst, usually a protein, that speeds up specific biochemical reactions in living organisms.

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Free Energy Change

The change in free energy that occurs during a reaction.

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Effect of Enzyme on Activation Energy

Enzymes lower the activation energy needed for a reaction to occur, speeding up the reaction without changing the overall free energy change.

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General Acid-Base Catalysis

The active site of an enzyme contains amino acids that act as proton donors or acceptors, facilitating acid-base catalysis.

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Covalent Catalysis

The active site of the enzyme interacts with the substrate to form an unstable temporary complex, enabling covalent reactions.

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Effect of Catalysis

The effect of enzymes on the activation energy, causing a decrease in the energy barrier.

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Enzymes Stabilize Transition State

The enzyme's ability to stabilize the transition state, which helps in lowering the activation energy.

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Conformational Change

A change in the tertiary or quaternary structure of an enzyme, which can alter its catalytic activity.

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Study Notes

Enzyme Action Mechanism

  • Enzymes act by forming a temporary complex with the substrate
  • The enzyme-substrate complex (ES) lowers the activation energy needed for the reaction
  • The substrate is converted into product(s)
  • The enzyme is unchanged after the reaction

Enzyme-Substrate Complex (ES)

  • The enzyme and substrate bind at the active site
  • The binding involves specific interactions (e.g., hydrogen bonds, ionic interactions)
  • The binding causes the substrate's shape to change slightly (induced fit model)

Michaelis-Menten Equation

  • Describes the relationship between substrate concentration, enzyme concentration and reaction rate
  • Defines the maximum velocity (Vmax) and the Michaelis constant (Km)
  • Km represents the substrate concentration at which the reaction rate is half of Vmax

Factors Affecting Enzyme Activity

  • Temperature: Optimum temperature exists, higher temperatures denature enzymes
  • pH: Enzymes have optimal pH values
  • Substrate concentration: Increasing substrate amount increases reaction rate to Vmax
  • Enzyme concentration: Higher enzyme concentration, faster reaction to Vmax
  • Inhibitors: Substances can inhibit enzyme activity (competitive or non-competitive)

Enzyme Structure and Function

  • Enzymes are proteins with a specific 3D structure
  • The active site is a crucial region for substrate binding
  • The active site's shape and chemical properties are unique to each enzyme, allowing it to catalyze only particular reactions
  • The active site's structure allows interactions with the substrate, facilitating the reaction

Enzyme Catalysis Mechanisms

  • Enzymes lower activation energy by bringing substrates together
  • Proximity: Orienting molecules properly to facilitate bonding
  • Straining the substrate: Altering substrate shape for easier bond breaking
  • General acid/base catalysis: Enzyme donates/accepts protons to alter substrate
  • Covalent catalysis: Enzyme forms temporary covalent bonds with substrate to increase reaction rate
  • Induced fit: the enzyme's active site molds to the substrate's shape

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Related Documents

Enzyme Mechanism PDF

Description

Explore the fascinating world of enzyme action mechanisms in biochemistry. This quiz covers the enzyme-substrate complex, the Michaelis-Menten equation, and factors affecting enzyme activity. Test your understanding of how enzymes function and their importance in biological reactions.

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