Which organelle manufactures and processes proteins before they are sent to the Golgi bodies?

• A. Ribosomes
• B. Endoplasmic Reticulum
• C. Lysosomes
• D. Vacuoles

Answer: (B)

Proteins are made on ribosomes, but the initial manufacturing and processing of those proteins take place in the rough endoplasmic reticulum. Ribosomes attached to the rough ER synthesize the polypeptides and thread them into the ER lumen, where they fold into proper shapes and may receive early modifications. Once this first processing is done, the proteins are packaged into vesicles and sent to the Golgi apparatus for further processing, sorting, and shipping to their final destinations. Lysosomes and vacuoles have other functions (digestion and storage, respectively), and free-floating ribosomes mainly synthesize proteins for use inside the cytosol, not for delivery to the Golgi.