Ribosomes and its Functions

Ribosomes

The outer membrane of the endoplasmic reticulum contain small granules commonly known as ribosomes, which are the smallest particulate components of the cytoplasm. They are rich in ribonucleic acids. Each ribosome has a large and a small subunit with a sedimentation constant of 50s and 30s respectively (Fig. 1.8). Each subunit contains about 65% RNA and 35% protein.

Functions

·        Ribosomes are the sites of protein synthesis. Messenger RNA binds in the groove between the subunits and specifies the sequence of amino acids in the growing polypeptide chains. The proteins synthesized on membrane bound ribosomes must pass successively through each of cytomembrane system.

·        Secretion may involve the fusion of the vacuoles with the plasma membrane followed by a discharge of the contents into the extra cellular space. This process is called exocytosis.