Which organelle is the site of protein synthesis?

• A. Ribosomes
• B. Endoplasmic Reticulum
• C. Nucleus
• D. Lysosome

Answer: (A)

Proteins are built by ribosomes, which read the genetic message on mRNA and link amino acids together to form a polypeptide. These small RNA-protein particles can float freely in the cytoplasm or be attached to the rough endoplasmic reticulum, where they synthesize proteins destined for secretion or for membranes. The actual assembly of amino acids happens at the ribosome, making it the primary site of protein synthesis. The endoplasmic reticulum helps process and fold proteins after synthesis and is involved in lipid production, the nucleus houses DNA and is where transcription occurs, and lysosomes digest and recycle materials. So, the organelle responsible for protein synthesis is the ribosome.