Question

Preventing the construction of amino acid cross-bridges between peptidoglycan chains is the mechanism of action of the _____________________________ antibacterial drugs.

Question 38 options:

	Beta lactams (penicillins)
	Aminoglycosides
	Imidazoles (Azoles)
	Tetracyclines
	Nucleotide analogues

Answer 1

The peptidoglycan is the constituent of the bacterial cell wall. It is a polymer which is composed of sugars and amino acids. The sugar moiety N-acetylglucosamine and N-acetylmuramic acid are alternatively linked by beta- (1,4) linkage. A peptide chain of an amino acid (ranges from three to five amino acids) is linked to N-acetylmuramic acids. These peptide chains of sugar strands are cross-linked to each other and form a mesh-like structural layer of the cell wall. It provides structural integrity and strength to the bacteria.

Preventing the construction of amino acid cross-bridges between peptidoglycan chains is the mechanism of action of the Beta-lactams (Penicillins) antibacterial drugs. The antibacterial drug Beta lactams (Penicillin) is the right answer. Penicillin prevents the cross-bridge formation between the peptidoglycan by inhibiting the enzymes which are involved in cross-bridge construction. Lack of amino acid cross-linking weakens the bacterial cell wall and leads to the rupture of the bacterial cells.

Aminoglycosides are antibacterial drug and their mode of action involve the inhibition of protein synthesis by interrupting elongation step of protein synthesis. Therefore, the aminoglycoside is not the right answer. Imidazole (azole) is a heterocyclic compound and mainly have antifungal activity. It causes DNA breakage which leads to cell death. Therefore imidazole is not the right answer. The antibacterial drug, tetracyclines inhibit protein synthesis by inhibiting the binding of charged aminoacyl-tRNA to the A-site of ribosome. Therefore, tetracycline is not the right answer. Nucleotide analogues are basically used as antiviral drugs, in treatment of cancer. Recent studies show that they can be used as an antibacterial drug. They utilize the replication process and when incorporated into the growing strand of DNA instead of nucleotide act as a chain terminator. Therefore, the nucleotide analogue is not the right answer.