Why do bacterial cells possess ribosomes?
Bacterial cells like eukaryotic cells possess ribosomes which are the sites of protein synthesis. The ribosomes consist of two subunits and each subunit further consists of protein and a type of RNA popularly called ribosomal RNA or rRNA.
The procaryotic ribosomes are 70 S ribosomes while in eucaryotic cells there are 80S ribosomes. Here S stands for Svedberg unit, named after its discoverer and is based on sedimentation under ultra-high speed centrifugation. The 70S ribosome comprises of small 30S subunits containing one molecule of r RNA and large 50 S subunits containing two molecules of ribosomal RNA. The antibiotics streptomycin, neomycin and tetracycline are effective because of their characteristic to inhibit protein synthesis on the ribosomes.