Which structure in a cell is responsible for protein synthesis?

The ribosome is the structure in a cell that is primarily responsible for protein synthesis. Ribosomes can be found freely floating in the cytoplasm or attached to the endoplasmic reticulum, and their main function is to translate messenger RNA (mRNA) into a polypeptide chain during the process of translation. This chain then folds into a functional protein.

While the nucleus plays a critical role in storing genetic information and producing mRNA through transcription, it does not directly synthesize proteins. The Golgi apparatus is involved in modifying, sorting, and packaging proteins for secretion or for use within the cell, but it does not synthesize proteins itself. The endoplasmic reticulum, particularly the rough endoplasmic reticulum, is where ribosomes are located and plays a supportive role in protein synthesis, but it is the ribosome that carries out the actual translation of mRNA into proteins. Therefore, the ribosome is the key site where protein synthesis occurs.