Q.Ribosomes found freely in the cytoplasm of a eukaryotic cell, and those attached to the rough endoplasmic reticulum, have a sedimentation coefficient of:

Ribosomes were first observed as dense granules by George Palade in 1953. They are non-membrane-bound organelles, the actual site of protein synthesis, built of two rounded subunits (about 60% RNA, 40% protein) held together by Mg2+ ions. Prokaryotic cells (and the mitochondria/chloroplasts of many algae and higher plants) carry the smaller 70S ribosome (30S + 50S subunits, three rRNA molecules: 16S, 23S and 5S); eukaryotic cytoplasmic ribosomes are the larger 80S type (40S + 60S subunits, four rRNA molecules: 18S, 28S, 5.8S and 5S). Ribosome/subunit size is expressed in Svedberg units, a sedimentation-rate-based measure named after Theodor Svedberg. When several ribosomes read one mRNA strand together they …