Chapter 10 Learning outcome

Question 1

Define Chemotherapeutic agents

Answer 1

Drugs that act against diseases

Question 2

Define Antimicrobial agents

Answer 2

Drugs that treat infections

Question 3

Define Semisynthetic agents

Answer 3

Chemically altered antibiotics that are more effective,
longer lasting, or easier to administer than naturally
occurring ones

Question 4

Define Synthetic agents

Answer 4

Antimicrobials that are completely synthesized in a lab

Question 5

Define Antibiotics

Answer 5

Antimicrobial agents produced naturally by organisms

Question 6

Explain how semisynthetic and synthetic antimicrobials differ from antibiotics.

Answer 6

Antibiotics are produced naturally from an organism. Semisynthetic antimicrobials are chemically altered antibiotics, and synthetic are completely synthesized in a laboratory.

Question 7

Provide some common antibiotics and semisynthetic agents and their sources

Answer 7

Penicillin: Originally derived from the fungus Penicillium, particularly Penicillium chrysogenum. It was the first antibiotic discovered by Alexander Fleming in 1928

Cephalosporins: These antibiotics are derived from the fungus Acremonium (formerly called Cephalosporium)

Ampicillin: A derivative of penicillin, it is synthesized from penicillin G.

Azithromycin: Semi-synthetic derivative of erythromycin.

Question 8

Mechanism of Antimicrobial Action: Explain the principle of selective toxicity

Answer 8

Selective toxicity- principle by which an effective antimicrobial agent must be more toxic to a pathogen than to the pathogen’s host

Question 9

Explain why antibacterial drugs constitute the greatest number and diversity of
antimicrobial drugs available.

Answer 9

because fungi, protozoa, and helminths-like their animal and human hosts- are eukaryotic chemoheterotrophs and share many common features.

Question 10

List and explain the six mechanism by which antimicrobial drugs affect pathogens.

Answer 10

1. drugs that inhibit cell wall synthesis: selectively toxic to certain fungal or bacterial cells, which have cell walls, but not to animals, which lack cell walls.
2. Drugs that inhibit protein synthesis (translation) by targeting the differences btwn prokaryotic and eukaryotic ribosomes.
3. Drugs that disrupt unique component of a cytoplasmic membraine
4. drugs that inhibit general metabolic pathways not used by humans
5. Drugs that inhibit nucleic acid synthesis
6. Drugs that blocks a pathogen’s recognition of or attachment to its host.

Question 11

inhibition of cell walls synthesis: Describe the actions and give examples of drugs that affect the cell walls of bacteria or fungi.

Answer 11

major structural component of bacterial cell wall is peptidoglycan later.
Actions:
1.Beta lactams- preventing the cross-linkage of NAM subunits
2. lipoglycopeptides- disrupt cell wall formation
3. bacitracin- blocks the transport of NAG and NAM across the cytoplasmic membrane to the wall.
4. Isoniazid and ethambutol- disrupt the formation of mycolic acid.

Question 12

Inhibition of synthesis of bacterial cell walls: Write all the different ways or mode of
actions of how drugs that inhibit the synthesis of bacterial cell walls are being designed to work.

Answer 12

• echinocandins- (caspofungin)
• inhibit the enzyme that synthesizes glucan;
• without glucan,
• fungal cells cannot make cell walls,
• leading to osmotic rupture.

Question 13

beta-lactams

Answer 13

-prevent cross-linkage of NAM subunits.

penicillin
cephalosporin
carbapenem

Question 14

Lipoglycopeptides

Answer 14

-disrupt cell wall formation
-directly interfere with particular alanine-alanine bridges that link the NAM subunits in many g(+) bacteria.
-vancomycin and cycloserine

Question 15

bacitracin

Answer 15

blocks the transport of NAG and NAM across the cytoplasmic membrane to the wall.

Question 16

isoniazid and ethambutol

Answer 16

disrupt the formation of mycolic acid.

Question 17

Inhibition of synthesis of fungal cell walls: Write one way or mode of action of how drugs that inhibit the synthesis of fungal cell walls are been designed to work.

Answer 17

1. echinocandins- (caspofungin),
2. inhibit the enzyme that synthesizes glucan
3. without glucan.
4. fungal cells cannot make cell walls.
5. leading to osmotic rupture.

Question 18

Define the term echinocandins as it relates to antimicrobial drugs.

Answer 18

Echinocandins are a group of originally natural antibiotics produced from a variety of fungal isolates that now have many semisynthetic derivatives. They inhibit synthesis of the major cross-linked glucan found exclusively in fungal cell walls by targeting β-1,3-d-glucan synthase.

Question 19

Inhibition of protein synthesis: Describe the actions and give examples of six antimicrobial drugs that interfere with ribosomes

Answer 19

1. Aminoglycosides and
2. tetracyclines- target 30s ribosomal subunit
3. chloramphenicol
4. Lincosamides or macrolides
5. antisense nucleic acid
6. oxazolidinone

Question 20

Interference with prokaryotic ribosomes: Write all the different ways or mode of actions of how drugs that inhibit protein synthesis are being designed to work

Answer 20

1. Binding to the Ribosome
2. Interference with tRNA Binding
3. Inhibition of Peptidyl Transferase
4. Disruption of Initiation or Elongation Factors
5. Disruption of Ribosome Assembly or Stability
6. Blocking mRNA Function
7. Induction of Ribosome Stalling

Question 21

Define aminoglycosides

Answer 21

Aminoglycosides are a class of antibiotics that inhibit bacterial protein synthesis by binding to the bacterial ribosome. They interfere with the translation process by causing misreading of mRNA and by inhibiting the initiation of protein synthesis. Aminoglycosides are effective against a wide range of gram-negative bacteria and some gram-positive bacteria.

Question 22

Define Lincosamides

Answer 22

Lincosamides are a class of antibiotics that inhibit bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome. This binding prevents the formation of peptide bonds between amino acids, thereby inhibiting the elongation of the polypeptide chain during translation.

Question 23

Define streptogramins

Answer 23

Streptogramins are a class of antibiotics that inhibit bacterial protein synthesis by binding to the bacterial ribosome. They interfere with translation by blocking the exit tunnel of the ribosome, preventing the elongation of the polypeptide chain

Question 24

Define macrolides

Answer 24

Macrolides are a class of antibiotics that inhibit bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome. They interfere with translation by blocking the movement of the ribosome along the mRNA, thereby preventing the elongation of the polypeptide chain. Macrolides are effective against a wide range of gram-positive and some gram-negative bacteria, as well as atypical pathogens.

Question 25

Define antisense nucleic acids

Answer 25

Antisense nucleic acids are synthetic nucleic acid molecules that are designed to bind to complementary sequences of mRNA. By binding to mRNA, antisense nucleic acids can block translation or promote degradation of the mRNA, ultimately leading to reduced expression of the target protein. Antisense nucleic acids have potential as antimicrobial agents by targeting essential bacterial genes, disrupting bacterial growth and survival.

Question 26

Define oxazolidinones

Answer 26

Oxazolidinones are a class of antibiotics that inhibit bacterial protein synthesis by binding to the 50S subunit of the bacterial ribosome. They interfere with translation initiation and prevent the formation of the initiation complex, thereby inhibiting protein synthesis. Linezolid is an oxazolidinone antibiotic commonly used to treat infections caused by multidrug-resistant gram-positive bacteria

Question 27

Interference with the charging of transfer RNA molecules: Write all the different ways or
mode of action for how drugs that inhibit protein synthesis are being designed to work.

Answer 27

1. inhibition of Aminoacyl-tRNA Synthetases
2. Disruption of Amino Acid Binding Sites
3. Altering tRNA Structure or Function:
4. Interference with Editing Mechanisms:
5. Induction of tRNA Misacylation:

Question 28

Disruption of cytoplasmic membranes: describe the actions of antimicrobial drugs
that interfere with cytoplasmic membranes.

Answer 28

Antimicrobial drugs that disrupt cytoplasmic membranes target the integrity and function of the cell membrane of microorganisms, causing leakage of cellular components and ultimately cell death.

Question 29

Write all the different ways or mode of actions of how drugs that disrupt
cytoplasmic membrane are being designed to work

Answer 29

1. Perturbation of Membrane Structure
2. Formation of Pores or Channels
   3.Disruption of Membrane Potential:
3. Altering Membrane Fluidity
4. Inhibition of Enzymatic Activity

Question 30

Inhibition of metabolic pathways: explain the action of antimicrobial drugs that
disrupt synthesis of folic acid.

Answer 30

Sulfonamides compete with PABA molecules for the active site involved in producing dihydrofolic acid, leading to a decrease in the production of THF and thus DNA and RNA

Question 31

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