Antimicrobial agents

Question 1

Describe how penicillin works

Answer 1

By binding to and preventing the action of transpeptidase enzymes which are required for the cross linking of the bacterial peptidoglycan cell wall.
This reduces cell wall strength and can lead to osmotic lysis. As cell wall synthesis is required for bacterial cell division, this is also prevented.

Question 2

What type of antibiotic is penicillin

Answer 2

A β-lactam antibiotic

Question 3

Describe tetracyclines

Answer 3

Tetracyclines are antibiotics which are composed of 4 fused rings, each with a different functional group granting tetracycline a broad spectrum of action.
Tetracylines reversibly bind to the 30S ribosomal sub-unit and block binding of RNA at the acceptor site, thus preventing protein synthesis. Because of reversible binding tetracycline is bacteriostatic not bacteriocidal

Question 4

How are some bacteria resistant to tetracycline

Answer 4

If they possess the TetA protein - this pumps tetracycline out of the cell

Question 5

Name mechanisms by which antiviral drugs may work

Answer 5

By inhibiting -attachment, cell penetration, uncoating, viral release or nucleic acid synthesis or inhibiting viral enzymes such as reverse transcriptase

Question 6

Describe acylcovir

Answer 6

Acyclovir an anti-viral drug which is a nucleoside analogue similar to guanine. When acyclovir is incorporated into a growing DNA chain it leads to termination of replication because it does not posses a 3’ OH group. It must first be phosphorylated by the viral enzyme thymidine kinase and thus only affects virally infected cells and is only affective against DNA viruses that possess thymidine kinase such as the herpes virus

Question 7

Describe remedesivir

Answer 7

An antiviral drug which is a ribonucleotide analogue that must be phophorylated in order to activate. When incorporated into a growing RNA chain it can stall rna polymerase or act as achain terminator