Which structure is responsible for protein synthesis in cells?

Ribosomes are the cellular structures responsible for protein synthesis. They can be found either free-floating in the cytoplasm or bound to the endoplasmic reticulum, forming what is known as rough ER. Ribosomes translate messenger RNA (mRNA) into polypeptide chains, which then fold into functional proteins. This process occurs in two stages: translation begins when ribosomes bind to mRNA, and it continues as the ribosome moves along the mRNA, adding the appropriate amino acids through transfer RNA (tRNA) until a complete protein is formed.

Other structures in the cell play vital roles in supporting protein synthesis but are not directly involved in the process itself. For example, the nucleus is primarily responsible for storing and transcribing genetic information, while the mitochondrion is the powerhouse of the cell, generating ATP through cellular respiration. The Golgi apparatus modifies, sorts, and packages proteins for secretion or delivery to other organelles, but again, it does not directly engage in the synthesis of proteins. Therefore, the ribosome is the key player in the actual production of proteins in a cell.