In which part of the cell does protein synthesis occur?

Protein synthesis primarily occurs at the ribosomes, which are cellular structures responsible for translating messenger RNA (mRNA) into polypeptide chains, ultimately forming proteins. Ribosomes can be found either floating freely in the cytoplasm or attached to the endoplasmic reticulum, which is then referred to as rough ER due to the presence of ribosomes on its surface. This process involves the assembly of amino acids in the order specified by the sequence of nucleotides in the mRNA transcript, making ribosomes essential to the cellular function and the overall process of gene expression.

Other cellular components listed are involved in different aspects of cellular function. The mitochondria produce energy through cellular respiration, while the nucleus contains the cell’s genetic material and is the site where transcription occurs, but not the actual synthesis of proteins. The Golgi apparatus is responsible for modifying, sorting, and packaging proteins synthesized by ribosomes before they are sent to their final destinations, either inside or outside the cell.