Which organelle processes and packages proteins?

• A. Golgi apparatus
• B. Rough endoplasmic reticulum
• C. Lysosome
• D. Vacuole

Answer: (A)

Proteins destined for secretion or for membranes are processed and packaged in the Golgi apparatus. After being made and folded in the rough endoplasmic reticulum, these proteins are transported in vesicles to the cis face of the Golgi. Inside the Golgi, they are further modified (for example, by adding sugar chains) and then sorted and packaged into new vesicles at the trans face. These vesicles then deliver the proteins to their final locations—such as the cell membrane, lysosomes, or outside the cell.

The other organelles aren’t primarily responsible for this packaging step: the rough endoplasmic reticulum synthesizes and begins folding proteins, lysosomes contain enzymes for digestion, and vacuoles mainly store substances.