Enzyme Specificity and Function
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Questions and Answers

What is the transition state in a chemical reaction?

  • A state where reactants are transformed into products
  • The energy needed to maintain a reaction
  • The point of maximum energy during a reaction (correct)
  • The energy required to start a reaction

    • What role do enzymes play in chemical reactions?

  • They convert products back to reactants
  • They reduce the activation energy needed for reactions (correct)
  • They increase the activation energy requirement
  • They directly participate in the chemical changes

    • Which type of specificity describes enzymes that act only on one specific substrate?

  • Absolute specificity (correct)
  • Relative specificity
  • Group specificity
  • Streospecificity

    • What defines relative specificity in enzyme action?

    <p>Acting on chemically related compounds but at different rates</p> Signup and view all the answers

    D-amino acid oxidase is an example of which type of enzyme specificity?

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

    Which enzyme is correctly matched with its substrate?

    <p>Lactase - Lactose</p> Signup and view all the answers

    How does pepsin demonstrate group specificity?

    <p>It targets specific peptide bonds in aromatic amino acids</p> Signup and view all the answers

    What describes the activation energy of a chemical reaction?

    <p>The energy needed to start the reaction</p> Signup and view all the answers

    What is a primary characteristic that distinguishes enzymes from inorganic catalysts?

    <p>Enzymes are specific in their reactions</p> Signup and view all the answers

    Which of the following correctly describes enzyme nomenclature?

    <p>Enzymes are usually named by adding –ase to the substrate name</p> Signup and view all the answers

    What is one way enzymes can exhibit their functionality?

    <p>They remain unchanged after the reaction</p> Signup and view all the answers

    What is the significance of the enzyme code (EC)?

    <p>It provides a systematic way to classify and describe enzymes</p> Signup and view all the answers

    How do enzymes typically achieve an increase in reaction rate?

    <p>By forming an enzyme-substrate complex</p> Signup and view all the answers

    What role do activators play in enzymatic activity?

    <p>They can enhance or facilitate enzyme activity</p> Signup and view all the answers

    What is a distinguishing property of inorganic catalysts compared to enzymes?

    <p>Inorganic catalysts do not require an activator</p> Signup and view all the answers

    Which of the following statements about enzyme action is correct?

    <p>Enzymes can participate in multiple reactions simultaneously</p> Signup and view all the answers

    What is the primary role of carboxypeptidase in peptide digestion?

    <p>Acting on the carboxylic end of a peptide chain</p> Signup and view all the answers

    Which factor does NOT affect enzyme activity?

    <p>Color of the enzyme</p> Signup and view all the answers

    What does the Michaelis-Menten constant (Km) represent?

    <p>The substrate concentration at half maximum velocity</p> Signup and view all the answers

    What type of specificity does an enzyme with dual specificity exhibit?

    <p>It acts on two different substrates producing two different products</p> Signup and view all the answers

    How does increasing enzyme concentration affect the reaction rate?

    <p>It increases the reaction rate until substrate is depleted</p> Signup and view all the answers

    Which of the following factors does NOT typically influence enzyme activity?

    <p>Shape of the enzyme</p> Signup and view all the answers

    What happens when the substrate concentration reaches Km?

    <p>50% of the active sites of the enzyme are occupied</p> Signup and view all the answers

    Which statement about isocitrate dehydrogenase is correct?

    <p>It acts on isocitrate producing ketoglutarate by decarboxylation and dehydrogenation</p> Signup and view all the answers

    What effect does the accumulation of reaction products have on enzymatic activity?

    <p>It decreases the enzymatic velocity.</p> Signup and view all the answers

    Which factor can lead to a decrease in enzymatic reaction over time?

    <p>Slight denaturation of enzyme.</p> Signup and view all the answers

    How do metal ions act as enzyme activators?

    <p>They bind to the enzyme to stabilize its structure.</p> Signup and view all the answers

    What distinguishes competitive reversible inhibitors from non-reversible inhibitors?

    <p>Competitive inhibitors can be displaced by substrate.</p> Signup and view all the answers

    What is one way enzymes can be activated by specific agents?

    <p>By removing inhibitory peptides.</p> Signup and view all the answers

    In what way can temperature affect enzyme activity?

    <p>Optimal temperatures increase the rate of reactions.</p> Signup and view all the answers

    What type of enzyme is carbonic anhydrase categorized as based on its metal ion?

    <p>Metalloenzyme.</p> Signup and view all the answers

    What is one effect of pH on enzyme activity?

    <p>Extreme pH levels can lead to denaturation of enzymes.</p> Signup and view all the answers

    Which statement is true about coenzymes?

    <p>They are loosely attached and can be easily dialyzed.</p> Signup and view all the answers

    What distinguishes holoenzymes from simple enzymes?

    <p>Holoenzymes contain both protein and non-protein components.</p> Signup and view all the answers

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

    <p>It binds substrates and facilitates chemical reactions.</p> Signup and view all the answers

    What type of group is referred to as a prosthetic group?

    <p>An inorganic cofactor firmly attached to the protein.</p> Signup and view all the answers

    Which of the following is an example of a prosthetic group?

    <p>Iron in catalase</p> Signup and view all the answers

    Which of the following best describes the nature of simple enzymes?

    <p>They are made up only of protein molecules.</p> Signup and view all the answers

    Which functional groups in enzymes are crucial for interacting with substrates?

    <p>Hydroxyl and sulfhydryl groups</p> Signup and view all the answers

    What happens in irreversible inhibition?

    <p>The inhibitor modifies the enzyme structure permanently.</p> Signup and view all the answers

    Which enzyme class is responsible for catalyzing oxidation-reduction reactions?

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

    Which of the following substances can act as irreversible inhibitors?

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

    How do oxidases function?

    <p>They use oxygen to accept electrons.</p> Signup and view all the answers

    Which one of the following is NOT classified under oxidoreductases?

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

    What characterizes suicide inhibitors?

    <p>They permanently deactivate the enzyme.</p> Signup and view all the answers

    Which type of oxidase forms hydrogen peroxide?

    <p>Xanthine oxidase</p> Signup and view all the answers

    What is the primary role of antienzymes like antitrypsin?

    <p>They irreversibly inhibit digestive enzymes.</p> Signup and view all the answers

    Study Notes

    Enzymes

    • Enzymes are protein catalysts produced by living cells.
    • They increase the rate of chemical reactions, but do not initiate them.
    • They function in all living systems without altering themselves.

    Difference between Prosthetic group and Coenzyme

    • Coenzyme: Loosely attached to or free, easily dialyzed and separated, contacts the enzyme only during reaction, always organic (often a vitamin B complex).
    • Prosthetic Group: Firmly attached to the protein, cannot be dialyzed or separated without enzyme destruction, always attached to the protein fraction, mostly inorganic (like Cu in tyrosinase, Zn in carbonic anhydrase, or iron porphyrin in catalase).

    Nature of Enzymes

    • Enzymes are protein in nature.
    • They are categorized into two types:
      • Simple enzymes: Composed solely of protein molecules, not bound to any non-protein groups.
      • Holoenzymes: Composed of protein molecules (apoenzyme) and bound to non-protein components (cofactor). Cofactors can be organic (coenzymes) or inorganic (prosthetic groups).

    Active Site

    • Enzyme molecules have specialized pockets called active sites.

    • Active sites have two regions:

      • Binding site: The substrate binds to the enzyme, forming an enzyme-substrate (ES) complex.
      • Catalytic site: The ES complex is converted to an enzyme-product (EP) complex, then dissociates into enzyme and products.

    • Each enzyme possesses one or more active centres.

    • The active site contains functional groups (e.g., hydroxyl of serine, phenolic of tyrosine, sulfhydryl of cysteine, or imidazole of histidine) that interact with the substrate.

    Difference between Enzyme and Inorganic Catalysts

    • Enzymes: Protein in nature, thermolabile (denatured by heat), specific in reactions, some require activators, activity due to specific groups, need little time.
    • Inorganic Catalysts: Vary in chemical structure, usually thermostable, non-specific, do not need activators, activity due to the whole system, require extra time.

    Enzyme Nomenclature

    • Enzymes often named by adding "‐ase" to the substrate name (e.g., urease, maltase, lactase).
    • Nomenclature can also be based on reaction type (e.g., oxidase, reductase, hydrolase).
    • Some enzymes have traditional names (e.g., pepsin, trypsin).
    • Others have names describing both their substrate and the reaction type (e.g., succinate dehydrogenase, pyruvate decarboxylase, and glutamine synthase).

    Enzyme Code (EC)

    • Each enzyme has a numerical code, the Enzyme Commission number (EC number), composed of four digits separated by dots.
    • The first digit indicates the enzyme class.
    • The second digit indicates the functional group of the enzyme.
    • The third digit indicates the coenzyme.
    • The fourth digit indicates the substrate.

    Enzyme Mechanism

    • Enzyme (E) combines with substrate (S) forming an enzyme-substrate (ES) complex.
    • The enzyme-substrate complex undergoes a reaction, forming an enzyme-product (EP) complex.
    • The enzyme and product (P) dissociate, releasing the product.
    • The enzyme is unchanged and can repeat the process.

    Factors Affecting Enzyme Activity

    • Substrate concentration: Increasing substrate concentration increases reaction rate up to a maximum.
    • Enzyme concentration: Reaction rate is proportional to enzyme concentration until substrate is depleted.
    • End product concentration: Accumulated end products decrease enzyme velocity.
    • Temperature: Optimum temperature for human enzymes is near 37°C. Higher temperatures denature enzymes, causing reaction rate to fall.
    • pH: Enzymes exhibit maximum activity within a narrow pH range called optimum pH.
    • Time: Enzymes decrease activity due to denaturation, accumulation of end products and substrate depletion.
    • Activators: Can increase enzyme reaction rate by various mechanisms like removing inhibitory peptides, or providing required metal ions.
    • Inhibitors: Substances that reduce enzyme activity; can be reversible (competitive, non-competitive, uncompetitive) or irreversible.

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    Description

    This quiz explores key concepts related to enzyme specificity and function in chemical reactions. Topics include transition states, enzyme roles, specificity types, and the importance of enzyme nomenclature. Test your understanding of how enzymes operate and their significance in biochemical processes.

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