Ribosomes were discovered by Robinson and Brown in plant cells and by Palade in animal cells.
Ribosomes are naked ribonucleoprotein protoplasmic particles (RNP) with a length of 200-340 Angstrom and diameter of 170-240 Angstrom which function as the sites for the protein or polypeptide synthesis.
Ribosomes are popularly known as protein factories. They are subspherical in the outline. A covering membrane is absent. Each ribosome consists of two unequal subunits, larger dome-shaped, and smaller oblate-ellipsoid.
The large subunit has a protuberance, a ridge, and a stalk. The smaller subunit possesses a platform, cleft, head, and base.