What is a defining feature of the Golgi apparatus?

• A. It has cis and trans surfaces.
• B. It is the site of ATP synthesis.
• C. It contains ribosomes on its surface.
• D. It is identical in all cell types with no polarity.

Answer: (A)

The defining feature is the polarized organization of the Golgi apparatus into cis and trans faces. The cis face sits near the endoplasmic reticulum and receives cargo in transport vesicles, while the trans face faces toward the plasma membrane and exports processed proteins in vesicles. As proteins move through the stacked cisternae (cis, medial, trans), they’re modified and sorted for final destinations. This cis–trans polarity is what sets the Golgi apart. By contrast, ATP synthesis occurs in mitochondria, ribosomes on the surface indicate rough ER, and the Golgi is not identical in all cell types nor devoid of polarity.