Exam II: Antibiotics

Question 1

Streptomyces, Bacillus, and Escherichia are examples of bacteria that produce what?

Answer 1

They produce antibiotics

Question 2

What are 2 molds that can produce antibioltics?

Answer 2

Penicillum, Cephalosporum

Question 3

What is selective toxicity?

Answer 3

Drugs that specifically target microbial processes, and do not harm the host cellular processes

Question 4

What are 5 mechanisms of action/sites of selective toxicity?

Answer 4

Bacterial cell wall
Nucleic acid synthesis
Protein synthesis
Cell membrane
Folic acid synthesis

Question 5

Why does interruption of folic acid synthesis work in targeting bacteria?

Answer 5

We bring our own folic acid into ourselves, but bacteria have to make it.

Question 6

How do penicillins and cephalosporins work in regard to cell wall synthesis?

Answer 6

Inhibits cross-linking by blocking peptidases within the NAG/NAM/pentapeptide stucture to weaken the cell wall and cause it to burst. No new crosslinks

Question 7

How does vancomycin work in regard to cell wall synthesis?

Answer 7

Hinders peptidoglycan elongation, which inhibits NAG/NAM linking

Question 8

How does cycloserine work in regard to cell wall synthesis?

Answer 8

Prevents the cell from making NAG/NAM subunits

Question 9

What happens when antibiotics weaken the cell wall?

Answer 9

The cell lyses

Question 10

What is Penicillin chrysogenum?

Answer 10

The mold where PCN was first discovered

Question 11

What generations of PCN are there?

Answer 11

1st, 2nd, 3rd

Question 12

What are natural forms of penicillin?

Answer 12

Penicillin G and V

Question 13

Ampiccilin and carbenicillin are examples of what?

Answer 13

Synthetic penicillin

Question 14

How are synthetic penicillins made?

Answer 14

A base unit penicillin undergoes a structure change in a lab.

Question 15

The basic structure of a penicillin consists of which 3 parts?

Answer 15

Thiazolidine ring
Beta-lactam ring
Variable side chain (R group)

Question 16

Which portion of the penicillin structure is responsible for the activity of the drug?

Answer 16

R group

Question 17

What portion of the penicillin structure is necessary to make the penicillin active?

Answer 17

Beta-lactam ring

Question 18

What does an active penicillin do to combat a microbe?

Answer 18

Inhibits peptidoglycan activity

Question 19

What does a penicillin resistant organism do to become resistant to make the penicillin ineffective?

Answer 19

B-lactamase (exoenzyme) secreted outside of cell and cleaves to the B-lactam ring. This inactivates the penicillin (since the B-lactam ring is necessary to be active).

Question 20

Penicillins (such as ampicillin) are ineffective on mycobacteria. Why?

Answer 20

Mycoplasmas lack a cell wall, which is how a penicillin works.

Question 21

What are cephalosporins similar to? What are 2 structural differences that cephalosporins have from the other?

Answer 21

Similar to penicillin. Differences include the main ring is different, and there are 2 sites for R groups.

Question 22

From what is cephalosporins made, and what kind of organism is it?

Answer 22

Cephalosporium acremonium (mold)

Question 23

How do aminoglycosides, tetracyclines, and chloramphenicol work?

Answer 23

They interfere with the process of translation

Question 24

How does tetracycline work? What is is commonly used for? What are benefits to its use? Side effects?

Answer 24

Inhibits protein synthesis. Used for STDs. It is broad spectrum and low cost. Can be used on both Gram + and Gram - organisms. May cause gastrointestinal disruption.

Question 25

What is the name for the drug in a Z-pak? How does it work? What is it commonly used for? What are benefits to its use?

Answer 25

Erythromycin. Inhibits protein synthesis. It is commonly used as prophylaxis prior to surgery. It is broad spectrum, and has low incidence of side effects.