What structure is primarily involved in protein synthesis?

The ribosome is primarily involved in protein synthesis because it serves as the site where amino acids are assembled into proteins based on the information encoded in messenger RNA (mRNA). During the process known as translation, ribosomes read the sequence of nucleotides in mRNA and facilitate the binding of transfer RNA (tRNA), which carries specific amino acids. This orchestrated process leads to the formation of polypeptide chains, ultimately folding into functional proteins.

While other structures mentioned have important roles, they do not directly engage in the synthesis of proteins. The nucleus contains the genetic material and is where transcription (the process of creating mRNA from DNA) occurs, but it does not synthesize proteins itself. The endoplasmic reticulum plays a key part in processing and transporting proteins but relies on ribosomes for their synthesis. Lysosomes are primarily involved in breaking down waste materials and cellular debris, not in protein creation.