Which structure acts as the site of protein synthesis?

The ribosome acts as the site of protein synthesis within the cell. Ribosomes are molecular machines that translate messenger RNA (mRNA) into polypeptide chains, which then fold into functional proteins. The process of protein synthesis, known as translation, occurs when ribosomes read the sequence of codons in the mRNA, bringing together the appropriate transfer RNA (tRNA) molecules that carry corresponding amino acids. This assembly of amino acids continues until a complete protein is formed.

While the nucleus is responsible for the transcription of DNA into mRNA, it does not directly engage in protein synthesis. The endoplasmic reticulum is involved in the modification and transport of proteins, and the Golgi apparatus further processes, sorts, and packages proteins for delivery to their functional destinations. However, the actual synthesis of the protein itself occurs exclusively at the ribosomes, making it the key structure for this critical biological process.