Enzyme Features and Reactions Quiz
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Questions and Answers

What role do enzymes play in biochemical reactions?

  • They function as inhibitors.
  • They serve as reactants.
  • They act as catalysts. (correct)
  • They convert energy.

    • In the process of forming an enzyme-substrate complex, what happens to the energy of activation (Ea)?

  • It increases, resulting in slower reactions.
  • It fluctuates based on temperature.
  • It remains unchanged, promoting stability.
  • It decreases, facilitating faster reactions. (correct)

    • Which model suggests that the enzyme and its substrate have a complementary shape?

  • Competitive Inhibition Model
  • Lock and Key Model (correct)
  • Allosteric Regulation Model
  • Induced-Fit Model

    • What is the purpose of the numbering system in enzyme classification?

    <p>To indicate the type of reaction catalyzed.</p> Signup and view all the answers

    What is a prosthetic group in relation to enzymes?

    <p>It is a non-protein part necessary for enzyme function.</p> Signup and view all the answers

    What describes the Induced-Fit Model of enzyme action?

    <p>Binding of the substrate induces a conformational change in the enzyme.</p> Signup and view all the answers

    Which of the following is NOT one of the six classes of enzymes as proposed by the International Union of Biochemistry?

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

    What happens to the enzyme after it catalyzes a reaction?

    <p>It is recovered unchanged.</p> Signup and view all the answers

    What characteristic makes phospholipids amphipathic molecules?

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

    Why are fats solid at room temperature?

    <p>They have a higher melting point than unsaturated fatty acids.</p> Signup and view all the answers

    What role does cholesterol play in animal cells?

    <p>It serves as a structural component of cell membranes.</p> Signup and view all the answers

    Which of the following is a component of the phospholipid bilayer?

    <p>Polar phosphate heads.</p> Signup and view all the answers

    What is the base structure of sterols?

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

    Which of the following describes the primary difference between saturated and unsaturated fatty acids?

    <p>Unsaturated fatty acids contain double bonds between carbon atoms.</p> Signup and view all the answers

    What is the primary role of allosteric enzymes in metabolic pathways?

    <p>To regulate multi-step reaction pathways through feedback inhibition</p> Signup and view all the answers

    What is the function of phosphatidylcholine (PC) in cell membranes?

    <p>To provide structural integrity and fluidity.</p> Signup and view all the answers

    Which molecule is most commonly associated with animals and humans?

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

    What initiates the conversion of zymogens to their active forms?

    <p>The removal of specific amino acid residues</p> Signup and view all the answers

    How do polar regulatory substances affect gene expression?

    <p>They activate receptors that initiate a cascade pathway</p> Signup and view all the answers

    What structural representation is commonly used for monosaccharides?

    <p>Fischer projection structure</p> Signup and view all the answers

    Which of the following is a characteristic of the Haworth structure of monosaccharides?

    <p>It results from an intramolecular reaction between carbonyl carbon and hydroxyl group</p> Signup and view all the answers

    Which type of carbohydrates are the simplest and regarded as the building blocks?

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

    What occurs when an allosteric enzyme is deactivated by feedback inhibition?

    <p>The enzyme's activity decreases as concentrations of the end product increase</p> Signup and view all the answers

    Which structure do monosaccharides adopt in biological systems?

    <p>Cyclic forms such as pyran and furan</p> Signup and view all the answers

    What does the notation C18:2Δ9,12 indicate about linoleic acid?

    <p>It has 18 carbon atoms and two double bonds at positions 9 and 12.</p> Signup and view all the answers

    Why do saturated fatty acids have higher melting points than unsaturated fatty acids?

    <p>Saturated fatty acids have linear structures promoting better molecular interactions.</p> Signup and view all the answers

    What charges do acylglycerides possess?

    <p>They are neutral in nature.</p> Signup and view all the answers

    What role do diacylglycerides (DAG) play in cells?

    <p>They act as signaling molecules in signal transduction.</p> Signup and view all the answers

    Which statement is true regarding the structure of unsaturated fatty acids?

    <p>They have cis- double bonds that result in a twisted shape.</p> Signup and view all the answers

    What is the unique characteristic of naturally-occurring fatty acids?

    <p>They have an even number of carbon atoms.</p> Signup and view all the answers

    What can be inferred about the melting point of stearic acid compared to linoleic acid?

    <p>Stearic acid has a higher melting point than linoleic acid.</p> Signup and view all the answers

    What is the primary function of triacylglycerides (TAG)?

    <p>To serve as the storage form of fatty acids.</p> Signup and view all the answers

    What are co-enzymes derived from?

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

    What happens to water-soluble vitamins in the body?

    <p>They must be consumed daily</p> Signup and view all the answers

    Which function do metal cofactors perform in an enzyme?

    <p>Induce specific lock geometry</p> Signup and view all the answers

    How does the proximity and orientation effect facilitate catalysis?

    <p>By minimizing activation energy</p> Signup and view all the answers

    What can prolonged deficiency in vitamin co-enzymes lead to?

    <p>Certain disorders</p> Signup and view all the answers

    What is the role of metals as cofactors in enzymes?

    <p>Coordinate with amino acids to stabilize enzyme structure</p> Signup and view all the answers

    What was traditionally theorized about enzyme-substrate interaction regarding the transition state?

    <p>Enzyme distorts the substrate towards the transition state</p> Signup and view all the answers

    What does the Collision Theory of Reaction state?

    <p>Colliding particles must have proper orientation and energy</p> Signup and view all the answers

    What does transition state stabilization involve in enzyme activity?

    <p>The transition state making better contacts with the enzyme's active site</p> Signup and view all the answers

    Which of the following accurately describes the role of electrostatic catalysis in enzyme activity?

    <p>It enhances electrostatic interactions through a desolvation effect</p> Signup and view all the answers

    How does acid-base catalysis enhance reaction rates in enzymatic processes?

    <p>Through a cascade of protonation and deprotonation events</p> Signup and view all the answers

    What characterizes covalent catalysis in enzymatic reactions?

    <p>Transient covalent bonds formed during the reaction</p> Signup and view all the answers

    Which amino acid residue is known to facilitate acid-base catalysis as a base catalyst?

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

    What is a key feature of the enzyme superoxide dismutase's active site?

    <p>It has charged functional groups that stabilize intermediates</p> Signup and view all the answers

    Which of the following components can form intermediate covalent bonds in enzyme activity?

    <p>Prosthetic groups such as B-vitamins and metals</p> Signup and view all the answers

    What is the primary result of desolvation in the active site of an enzyme?

    <p>Lowered local dielectric constant enhancing electrostatic interactions</p> Signup and view all the answers

    Study Notes

    Enzyme Features and Reactions

    • Enzymes are globular proteins that catalyze biochemical reactions.
    • The active site is the region within the enzyme where the substrate binds.
    • The enzyme-substrate complex forms, lowering the activation energy, facilitating a faster reaction.
    • The enthalpy of the reaction remains constant.
    • Enzyme kinetics studies the reaction velocity.

    Enzyme Models

    • Lock and Key Model: Enzyme and substrate have complementary shapes. Substrate fits into the active site like a key into a lock.
    • Induced Fit Model: Initially loose binding of the substrate induces a conformational change in the enzyme, resulting in a tighter fit.

    Enzyme Classification

    • Enzymes are categorized based on the reaction they catalyze.

    • Six major classes:

      • Oxidoreductases: Oxidation-reduction reactions
      • Transferases: Transfer of a chemical group
      • Hydrolases: Bond breakage by addition of water
      • Lyases: Bond breakage without water addition
      • Isomerases: Intramolecular rearrangements/isomerization
      • Ligases: Bond formation by joining two molecules.

    • Enzymes are numbered using a four-digit code (e.g., 4.3.2.1). The first number represents the major class.

    Enzyme Prosthetic Groups

    • Prosthetic groups (co-enzymes and co-factors) are non-protein components necessary for enzyme function.
    • Vitamins (e.g., B-complex, Vitamin C) serve as co-enzymes, not stored in the body.
    • Minerals or metals (e.g., zinc) serve as co-factors.

    Mechanisms of Enzyme Catalysis

    • Proximity and Orientation Effect: Substrates brought together at the active site, properly oriented for efficient reaction.
    • Transition State Stabilization: The enzyme stabilizes the transition state, making the reaction more favorable.
    • Electrostatic Catalysis: Water exclusion at the hydrophobic active site lowers dielectric constant, enhancing electrostatic interactions.
    • Acid-Base Catalysis: Amino acid side chains act as proton donors or acceptors, changing substrate reactivity.
    • Covalent Catalysis: Transient covalent bonds form between enzyme and substrate.
    • Metal Ion Catalysis: Metal ions can bind substrates, facilitate electron transfer, or stabilize charges.

    Enzyme Regulation

    • Compartmentation: Enzymes localized in specific organelles.
    • Covalent Modification: Phosphate addition or removal alters enzyme activity.
    • Allosteric Regulation: Binding of effectors (molecules) alters enzyme conformation and activity.
    • Proteolytic Activation: Cleavage of inactive precursor (zymogen) to activate enzyme.
    • Transcriptional Control: Gene regulation controls enzyme production.

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    Description

    Test your knowledge on enzymes, their features, and the various models explaining their function. This quiz covers enzyme classification, reaction mechanisms, and kinetics, allowing you to explore how enzymes catalyze biochemical reactions effectively.

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