Which cellular structure is primarily responsible for protein synthesis?

The primary cellular structure responsible for protein synthesis is ribosomes. Ribosomes play a crucial role in translating messenger RNA (mRNA) into polypeptide chains, which ultimately fold into functional proteins. They can be found either floating freely in the cytoplasm or attached to the endoplasmic reticulum, known as the rough ER, where they facilitate the assembly of proteins that are either secreted from the cell or incorporated into cellular membranes.

In contrast, mitochondria are known as the powerhouse of the cell, generating ATP through cellular respiration, while the nucleus houses the cell's genetic material and serves as the control center for gene expression. Lysosomes contain enzymes necessary for breaking down waste materials and cellular debris, but they do not play a direct role in synthesizing proteins. Understanding the distinct functions of these cellular structures highlights the specific role of ribosomes in the fundamental process of protein synthesis.