The part of the cell responsible for protein synthesis is the ribosome. Ribosomes can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER. They translate the information encoded in messenger RNA (mRNA) into polypeptide chains, which fold into functioning proteins. This process is essential for cellular function and growth, as proteins perform various roles including acting as enzymes, structural components, and signaling molecules.