Which organelle is composed of RNA and protein; site of protein synthesis?

• A. Golgi bodies
• B. Ribosome
• C. Organelle
• D. Lysosomes

Answer: (B)

Protein synthesis happens on ribosomes, which are RNA–protein complexes. These tiny particles are built from ribosomal RNA and proteins and act as the machines that translate the genetic message in mRNA into a growing polypeptide chain. Ribosomes can float freely in the cytoplasm or attach to the rough endoplasmic reticulum, reflecting how the cell organizes protein production for different destinations. The Golgi apparatus and lysosomes perform other roles—modifying and shipping proteins, or breaking down cellular components—so they aren’t the sites where polypeptides are first made. The term organelle is too broad here; ribosomes are the specific structure responsible for protein synthesis.