Antibiotics

Question 1

how are antimicrobial drugs classified

Answer 1

they can be classified based on their molecular structure, mechanisms of action and their spectrum of activity

Question 2

what is the structure if penicillin

Answer 2

contains an N-Acyl group, a beta-lactam ring and a Thialozidine ring

Question 3

what kind of bacteria does penicillin act on

Answer 3

mostly gram positive bacteria

Question 4

what is transpeptidase

Answer 4

a protein that joins the chains of peptidoglycan together. they are also known a penicillin binding proteins

Question 5

how do beta lactams work

Answer 5

the beta lactam ring is the same shape as the chains that hold beta peptidoglycan layers together in the bacterial cell wall. This means that transpeptidase will bind to the lactam ring and become inhibited and is unable to synthesise the cell wall.

Question 6

what are beta lactamases

Answer 6

beta lactamases are proteins that can break down beta-lactam antibiotics resulting in resistance.

Question 7

what are the two main mechanisms by which bacteria can become resistant

Answer 7

They can alter the proteins that are inhibited by the antibiotics so they no longer bind
They can produce enzymes that break down the antibiotics so that they cannot inhibit other proteins.

Question 8

what is vancomycin

Answer 8

it is an antibiotic of last resort which binds to the chains holding the peptidoglycan layers of the bacterial cell wall together. this stops the transpeptidase from binding.

Question 9

how is protein synthesis inhibited by antibiotics

Answer 9

Macrolide antibiotics like Erythromycin and Tetracycline can bind directly to the ribosomal subunits, preventing the ribosomal complex from forming, the bacteria which inhibits translation. This is effective against both gram positive and gram negative bacteria.

Question 10

why do antibiotics that target bacterial ribosomes not effect humans cells

Answer 10

bacterial ribosomes (50s and 30s) are smaller than eukaryotic ribosomes (60s and 40s). They are still selective drugs

Question 11

how to bacteria gain resistance to ribosome targeting antibiotics

Answer 11

-Efflux proteins constantly pump antibiotic proteins outside of the cell.
-the target protein could mutate and no longer interact with the antibiotic
-the shape of the targeted protein can be changed by enzyme factors or other molecules
-the antibiotic can have its shaped changed by other molecules
-the antibiotic can be degraded by enzymes

Question 12

how can antibiotics inhibit DNA synthesis

Answer 12

the antibiotics called Quinolones bind to DNA gyrase (the protein that keeps DNA from supercoiling during transcription) and prevent it from acting.