Enzymes and Their Classification
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Questions and Answers

What are enzymes?

Enzymes are organic catalysts produced by living cells.

What is the function of enzymes in biological systems?

Enzymes accelerate a wide variety of chemical reactions which occur in biological systems.

Enzymes are biocatalysts.

True (A)

What is the common suffix used in enzyme names?

<p>The common suffix 'ase' is attached to the substrate of the reaction when naming enzymes.</p> Signup and view all the answers

What are the six major classes of enzymes?

<p>Transferases (A), Oxidoreductases (B), Isomerases (C), Lyases (D), Ligases (E), Hydrolases (F)</p> Signup and view all the answers

Oxidoreductases catalyze ______ reactions.

<p>redox</p> Signup and view all the answers

What do Transferases do?

<p>Transferases transfer functional groups between donors and acceptors.</p> Signup and view all the answers

What is the function of Hydrolases?

<p>Hydrolases catalyze the hydrolysis of substrates.</p> Signup and view all the answers

What reactions are catalyzed by Lyases?

<p>Lyases catalyze removal of a group other than hydrolysis.</p> Signup and view all the answers

What is the function of Isomerases?

<p>Isomerases catalyze inter-molecular rearrangement.</p> Signup and view all the answers

What do Ligases do?

<p>Ligases catalyze the union of two molecules.</p> Signup and view all the answers

Enzymes are made of proteins.

<p>True (A)</p> Signup and view all the answers

Enzymes are only present in some living cells.

<p>False (B)</p> Signup and view all the answers

What are some of the factors that can affect enzyme activity?

<p>Cellular conditions (A), Substrate concentration (B), pH (C), Temperature (D)</p> Signup and view all the answers

What is the active site of an enzyme?

<p>The active site is a special pocket or cleft on an enzyme molecule where the substrate binds.</p> Signup and view all the answers

How does the substrate bind to the enzyme?

<p>The substrate binds to the enzyme, forming an enzyme-substrate (ES) complex.</p> Signup and view all the answers

Enzyme-catalyzed reactions are highly efficient.

<p>True (A)</p> Signup and view all the answers

What is the turnover number, or kcat, of an enzyme?

<p>The turnover number, or kcat, represents the number of substrate molecules an enzyme converts to product per second.</p> Signup and view all the answers

Enzymes are highly specific, meaning they typically interact with only one or a few substrates.

<p>True (A)</p> Signup and view all the answers

How do the enzymes in a cell determine its metabolic pathways?

<p>The set of enzymes made in a cell determines which metabolic pathways occur in that cell.</p> Signup and view all the answers

What are Holoenzymes?

<p>Holoenzymes are active enzymes that consist of both a protein component (apoenzyme) and a non-protein component called a cofactor.</p> Signup and view all the answers

What is an Apoenzyme?

<p>An Apoenzyme is the protein component of an enzyme that is inactive without its non-protein cofactor, such as a metal ion or a small organic molecule.</p> Signup and view all the answers

What is a cofactor?

<p>A cofactor is a non-protein component of an enzyme that helps the enzyme function.</p> Signup and view all the answers

What is the main function of Coenzymes?

<p>Coenzymes are small organic molecules that act as cofactors, and they often derive from vitamins.</p> Signup and view all the answers

Enzyme activity can be regulated.

<p>True (A)</p> Signup and view all the answers

Many enzymes are localized in specific organelles within the cell.

<p>True (A)</p> Signup and view all the answers

What is the advantage of compartmentalization of enzymes?

<p>Compartmentalization helps isolate reaction substrates and products, preventing competition from other reactions and creating a favorable environment for specific processes within the cell.</p> Signup and view all the answers

What are the two main theories that describe how an enzyme binds to a substrate?

<p>The two theories are the Lock-and-Key theory and the Induced Fit Theory.</p> Signup and view all the answers

What is the Lock-and-Key Theory of enzyme action?

<p>The Lock-and-Key Theory proposes that the shape of the active site is pre-determined and complementary to the substrate, like a key fitting into a lock.</p> Signup and view all the answers

What is the Induced Fit Theory of enzyme action?

<p>The Induced Fit Theory states that the active site is flexible, and its shape changes to fit the substrate upon binding, causing a tighter and more efficient interaction.</p> Signup and view all the answers

What factors influence enzyme activity?

<p>All of the above (D)</p> Signup and view all the answers

What happens to enzyme activity as substrate concentration increases?

<p>Enzyme activity increases as substrate concentration increases, until a maximal velocity (Vmax) is reached.</p> Signup and view all the answers

How does temperature affect enzyme activity?

<p>Generally, enzyme activity increases with temperature until an optimal temperature is reached, beyond which the enzyme can denature and lose its activity.</p> Signup and view all the answers

What is the effect of pH on enzyme activity?

<p>Each enzyme has an optimal pH range where it functions best. Outside this range, enzyme activity decreases, and excessive deviations in pH can denature the enzyme.</p> Signup and view all the answers

What is an inhibitor?

<p>An inhibitor is a substance that can decrease the velocity of an enzyme-catalyzed reaction.</p> Signup and view all the answers

What is the difference between reversible and irreversible inhibitors?

<p>Irreversible inhibitors form strong, covalent bonds to the enzyme and permanently inactivate it. Reversible inhibitors bind less tightly to the enzyme and can be dissociated, allowing the enzyme to regain activity.</p> Signup and view all the answers

What is competitive inhibition?

<p>Competitive inhibition occurs when the inhibitor and substrate compete for the same binding site on the enzyme.</p> Signup and view all the answers

What is noncompetitive inhibition?

<p>Noncompetitive inhibition occurs when the inhibitor binds to a different site on the enzyme than the substrate, but still affects the enzyme's activity.</p> Signup and view all the answers

Flashcards

Biocatalyst

An enzyme; a catalyst produced by a living organism.

Enzyme Suffix

The suffix '-ase' is typically added to the substrate to form the enzyme name.

Enzyme Nomenclature

A systematic way of naming enzymes based on the substrate or reaction.

Enzyme

A biological catalyst, accelerating chemical reactions in living organisms.

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Active Site

The specific region of an enzyme where the substrate binds.

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Substrate

The molecule upon which an enzyme acts.

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Enzyme-Substrate Complex

The temporary intermediate complex formed when the enzyme binds to the substrate.

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Catalytic Efficiency

How quickly an enzyme converts substrate to product.

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Turnover Number (kcat)

The number of substrate molecules converted to product per enzyme molecule per second.

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Specificity

Enzymes' ability to target specific substrates and reactions.

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Holoenzyme

The complete, active enzyme including its non-protein component.

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Apoenzyme

The protein part of an enzyme without its non-protein component.

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Cofactor

A non-protein component, often a metal ion, needed for enzyme activity.

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Coenzyme

A small organic molecule, often derived from vitamins, needed for enzyme activity.

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Enzyme Regulation

Controlling the activity of enzymes based on cellular needs.

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Cellular Localization

Enzymes are often located in specific parts of a cell.

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Lock and Key Theory

The active site of an enzyme is a perfect fit for its substrate.

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Induced Fit Theory

The active site changes shape to bind to the substrate.

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Substrate Concentration

Rate of reaction increases with substrate, then plateaus.

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Temperature Effect

Enzymes have optimal temperatures; higher temperatures denature them.

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Vmax

The maximum reaction rate of an enzyme.

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pH

A measure of acidity/alkalinity; affects enzyme activity.

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Study Notes

Enzymes

  • Enzymes are organic catalysts produced by living cells.
  • They accelerate various chemical reactions in biological systems.
  • Enzymes are also known as biocatalysts.

Enzyme Nomenclature

  • Common names usually end with "-ase" and are linked to the substrate of the reaction.
    • Example: Urea -> Urease, Lactose -> Lactase.
  • Other enzymes are named after their substrate and the catalysed reaction.
    • Example: Lactate dehydrogenase, Pyruvate decarboxylase.
  • Some enzyme names are historical and don' t directly relate to the substrate or reaction.
    • Example: Catalase, Pepsin, Chymotrypsin, Trypsin.

Enzyme Classification

  • Enzymes are categorized into six major classes in the systematic naming system.
    • Oxidoreductases: Catalyze redox reactions.
    • Transferases: Transfer functional groups between donors and acceptors.
    • Hydrolases: Catalyze hydrolysis of substrates.
    • Lyases: Catalyze the removal of a group from a substrate, other than by hydrolysis.
    • Isomerases: Catalyze intermolecular rearrangements.
    • Ligases: Catalyze the union of two molecules.

Enzyme Properties

  • Enzymes are made of protein.
  • Present in all living cells.
  • Convert substrates into products.
  • Affected by cellular conditions (e.g., temperature, pH). Any condition impacting protein structure can impact enzyme function.

Active Sites

  • Enzymes have specialized pockets/clefts called active sites.
  • Active sites contain amino acid side chains that create a 3D surface complementary to the substrate.
  • Substrate (S) binds to the enzyme, forming an enzyme-substrate (ES) complex.
  • ES complex converts to an enzyme-product (EP) complex, then dissociates to release enzyme and product.

Catalytic Efficiency

  • Enzyme-catalyzed reactions are significantly faster than uncatalyzed reactions (103 to 108 times faster).
  • Each enzyme molecule can transform 100-1000 substrate molecules into product per second.
  • Turnover number (kcat) measures the number of substrate molecules an enzyme converts to product per second.

Enzyme Specificity

  • Enzymes are highly specific, interacting with one or a few substrates and catalyzing only one type of chemical reaction.
  • The specific set of enzymes in a cell determines possible metabolic pathways.

Holoenzymes

  • Some enzymes require non-protein components for activity.
  • Holoenzyme is the complete, active enzyme with its non-protein component.
  • Apoenzyme is the enzyme without its non-protein component - inactive.
  • Cofactors are metal ions (e.g., Zn2+, Fe2+)
  • Coenzymes are small organic molecules, often derived from vitamins (e.g., NAD, FAD).

Enzyme Regulation

  • Enzyme activity can be controlled (increased or decreased) to align with cellular needs.

Enzyme Localization

  • Enzymes are often located in specific organelles inside cells.
  • Organelle localization: Isolates reaction substrates/products from competing reactions.
  • Organelles also organize enzyme pathways. Examples given are mitochondria, cytosol, nucleus, and lysosome.

Enzyme Action Theories

  • Lock-and-Key Theory: The active site shape precisely complements the substrate.
  • Induced-Fit Theory: The enzyme's active site changes shape to fit the substrate.

Factors Affecting Enzyme Activity

  • Substrate concentration: Increasing substrate concentration increases the reaction rate until the enzyme is saturated.
  • Temperature: Optimal temperature increases reaction rate, though extreme temperatures cause denaturation.
  • pH: Different enzymes have specific pH optima for maximum activity, due to ionization status of amino groups, and extreme pH affects enzyme conformation. (Denaturation)

Enzyme Inhibition

  • Inhibitors diminish the velocity of enzyme-catalyzed reactions.
    • Irreversible Inhibitors: Bind covalently to enzymes.
    • Reversible Inhibitors: Bind non-covalently; the inhibitor is released upon dilution.
      • Competitive Inhibitors: Bind to the active site, competing with the substrate.
      • Noncompetitive Inhibitors: Bind to a different site, altering the enzyme's shape.

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Enzymes Introduction PDF

Description

Dive into the fascinating world of enzymes, the organic catalysts produced by living cells. Learn about their nomenclature, classification, and various functions in biological systems. This quiz will test your understanding of enzymatic processes and names.

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