Tetracycline inhibits protein synthesis by-

Ans. is 'b' i.e., Binding to 30 S subunit and inhibits binding of ami noacyl tRNA Tetracyclineso Tetracyclines are classified into three groups -# Group 1 - Tetracycline, oxytetracycline, chlortetracycline.# Group II - Lymecycline, Demeclocycline.# Group III - Minocycline, Doxycycline.o Tetracyclines are bacteriostatic and broad spectrum antibiotics.o Tetracycline interact with small ribosomal subunits, blacking access of aminoacyl- tRNA to the nuRNA-ribos- ome complex.o Oral absorption of tetracyclines is impaired by food except doxycycline and minocycline which are absorbed completely irrespective of food.o Most tetracyclines are primarily excreted in urine by glomerular filtration; dose has to be reduced in renal failure; doxycycline is an exception - doxycycline can be used in renal failure.o Tetracyclines can cross placenta and secreted in milk - contraindicated during pregnancy and lactation.