Which structure serves as the site of protein synthesis in cells?

The ribosome is the site of protein synthesis in cells. It plays a crucial role in translating messenger RNA (mRNA) into polypeptide chains, which then fold into functional proteins. Ribosomes can be found freely floating in the cytoplasm or attached to the endoplasmic reticulum, which further facilitates protein processing and transport.

Understanding the role of ribosomes in protein synthesis is fundamental because they are the cellular machinery that interprets the genetic code carried by mRNA, linking amino acids together in the correct order to form proteins. This process is essential for numerous cellular functions, from enzyme activity to structural roles in cells.

In contrast, while the nucleus is involved in the storage of genetic material and the transcription of DNA to mRNA, it is not directly involved in the synthesis of proteins. Mitochondria primarily function in energy production through respiration, and while the endoplasmic reticulum is involved in processing and transporting proteins, it is the ribosome that actually carries out the synthesis. Thus, the ribosome remains the central agent of protein assembly in the cell.