Ribosomes are the smallest granules, found in the cytoplasm, contain ribosomal RNA (rRNA) and many ribosomal proteins. On the basis of sedimentation coefficient they are of ret types-
(i) 70S ribosomes-They are smaller in size and their sedimentation coefficient is (found in bacteria and chloroplast).
(ii) 80S ribosomes-Their sedimentation coefficient is 80S and are found in higher plants and animals or eukaryotic cells In 80S ribosome, the larger subunit is 60S and smaller one 40S.