Enzymatic Inactivation by Steric Hindrance Quiz
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Questions and Answers

What is the primary function of β-lactamases?

  • Inactivate β-lactam antibiotics (correct)
  • Promote cell wall cross-linking
  • Enhance bactericidal activity
  • Stimulate enzyme regeneration
  • How does the hydrolytic regeneration of the active site in β-lactamases compare to cell wall transamidase?

  • Less efficient
  • Equally efficient
  • More efficient (correct)
  • Non-existent
  • Where are β-lactamases usually shed in gram-positive bacteria like staphylococci?

  • Directly into the medium
  • Outside the cell wall (correct)
  • Into the cytoplasm
  • Into the periplasmic space
  • What is a common expression of allergy to penicillin-type antibiotics?

    <p>Mild drug rash or itching</p> Signup and view all the answers

    How does the allergenic reaction to penicillin-type antibiotics vary?

    <p>Delayed or immediate onset</p> Signup and view all the answers

    What is the term used to classify an inhibitor that inhibits an enzyme irreversibly by undergoing subsequent reactions?

    <p>Mechanism-based inhibitor</p> Signup and view all the answers

    Which compound enhances the potency against β-lactamase–producing strains when added to amoxicillin and ticarcillin preparations?

    <p>Clavulanic acid</p> Signup and view all the answers

    How is sulbactam prepared?

    <p>By partial chemical synthesis from penicillins</p> Signup and view all the answers

    Which functional group substitution in ticarcillin enhances its water solubility and potency against gram-negative organisms?

    <p>Carboxylic acid moiety</p> Signup and view all the answers

    Which is a popular combination used clinically to combat β-lactamase-producing strains?

    <p>Clavulanic acid and ampicillin</p> Signup and view all the answers

    What is the primary reason for the defective cell wall and inactivated enzyme due to β-lactam antibiotics?

    <p>Steric hindrance preventing regeneration of the active site</p> Signup and view all the answers

    Why is water considered an insufficiently effective nucleophile in relation to cell wall transamidase inactivation by β-lactam antibiotics?

    <p>Steric barrier preventing hydrolysis of the complex</p> Signup and view all the answers

    What contributes to the structural weakness of the resulting cell wall under the action of β-lactam antibiotics?

    <p>Covalent interruption due to enzyme inactivation</p> Signup and view all the answers

    Why is resistance to β-lactam antibiotics alarming?

    <p>Mutated PBP-2 (PBP-2a) with decreased drug binding</p> Signup and view all the answers

    In the context of β-lactam resistance, what is the more common mechanism than decreased cellular uptake or lower binding affinity to protein binding proteins?

    <p>Production of β-lactamases</p> Signup and view all the answers

    What is the principal cause of bacterial resistance to beta-lactam antibiotics in the clinic?

    <p>β-lactamase catalyzed hydrolysis</p> Signup and view all the answers

    What are the products formed when alcohols and amines react with beta-lactam antibiotics?

    <p>Esters and amides</p> Signup and view all the answers

    How do proteins contribute to the formation of antigenic conjugates responsible for many penicillin allergies?

    <p>Through a specific primary amino group reaction</p> Signup and view all the answers

    What term is used for small molecules that react with proteins to produce antigens?

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

    Why is the hydrolysis of the beta-lactam ring significant for the deactivation of beta-lactam antibiotics?

    <p>To prevent reclosure to penicillin</p> Signup and view all the answers

    What modification to the cephalosporin structure leads to improved stability towards beta-lactamase?

    <p>Addition of a 7-alpha methoxyoxime</p> Signup and view all the answers

    Which modification is essential for the antimicrobial activity of cephalosporins?

    <p>Addition of an amino group at the alpha position</p> Signup and view all the answers

    What structural change is responsible for improved antibacterial activity in cephalosporins?

    <p>Replacement of the hydrogen at C-7 with an alkoxy group</p> Signup and view all the answers

    Which structural feature contributes to blocking the inhibitor's affinity for the enzyme?

    <p>Incorporation of a lactone ring</p> Signup and view all the answers

    Which modification results in improved stability of the beta-lactam in cephalosporins under acidic conditions?

    <p>Addition of an amino group at the alpha position</p> Signup and view all the answers

    What is the molecular mode of action of beta-lactam antibiotics?

    <p>Inhibition of enzymes processing peptidoglycan layer</p> Signup and view all the answers

    In the context of cell wall cross-linking, what role do penicillin-binding proteins (PBPs) play?

    <p>Facilitating cross-linking of the cell wall peptidoglycan</p> Signup and view all the answers

    What is the major mechanism by which beta-lactam antibiotics exhibit bactericidal activity?

    <p>Inhibiting cell wall synthesis through enzyme inactivation</p> Signup and view all the answers

    Which structural feature contributes to the resistance of nafcillin and dicloxacillin to enzyme degradation?

    <p>D-alanine-d-alanine unit termination</p> Signup and view all the answers

    What is the primary consequence of β-lactam antibiotics reacting with penicillin-binding proteins (PBPs) according to Path B?

    <p>Inhibition of cell wall cross-linking</p> Signup and view all the answers

    What is the enzyme responsible for metabolizing imipenem through hydrolysis of the β-lactam, deactivating it?

    <p>Renal dehydropeptidase-1</p> Signup and view all the answers

    Which carbapenem has a chiral methyl group at C-4, conferring intrinsic resistance to hydrolysis by dehydropeptidase-1?

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

    What is the inhibitor coadministered with imipenem to protect it from metabolic deactivation by renal dehydropeptidase-1?

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

    Which carbapenem is considered more potent against Pseudomonas species compared to imipenem and meropenem?

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

    What synthetic monocyclic β-lactam antibiotic has an antimicrobial spectrum devoted almost exclusively to gram-negative microorganisms?

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

    Which carbapenem is not active against Pseudomonas or Acinetobacter?

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

    What group confers stability toward dehydropeptidase-1 for both doripenem and ertapenem?

    <p>4-β-methyl group</p> Signup and view all the answers

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