proteins are synthesised on which sub-cellular structure?

Proteins are synthesized on the ribosomes , which are the primary sub- cellular structures responsible for protein synthesis. Ribosomes can be found either freely floating in the cytoplasm or attached to the rough endoplasmic reticulum (ER) in eukaryotic cells. The mRNA is translated into protein at the ribosomes, where amino acids are linked together to form polypeptide chains. The rough ER, studded with ribosomes, plays an important role in processing proteins within the cell. Thus, ribosomes—both free and bound to rough ER—are the sites of protein synthesis in cells.