A Golgi cisterna is a flattened membrane-enclosed sac. Stacking several sacs does not make their interiors one open space: membrane separates Golgi lumen from intervening cytosol.[ref]
The Golgi Apparatus. The Cell: A Molecular Approach, 2nd edition by Geoffrey M. Cooper; Organization of the Golgi, Figure 9.22: membrane-enclosed cisternae
The Golgi lumen is the enclosed interior of a Golgi cisterna, distinct from the surrounding cytosol.
The membrane-sidedness rule in secretory protein routing still applies within the Golgi apparatus. For a local worked example, stipulate a membrane protein with a carbohydrate chain exposed to Golgi lumen and a tail exposed to cytosol. An enzyme confined to Golgi lumen can contact that chain, but cannot directly contact the cytosolic tail without a boundary-crossing step. A change in which Golgi cisterna contains the protein need not turn the protein over. Thus chemical accessibility and cargo location are different questions: moving cargo onward preserves its membrane sides under the budding and fusion operations described in secretory protein routing.
Articles by others on the same topic
There are currently no matching articles.