What is a Golgi Apparatus?
1 Answer
Good answer in the video... However...
Explanation:
Some proteins will be membrane spanning, that is, not all proteins are in the lumen in the ER.
In the Golgi, the cis face is formed from the fussion of vesicles that bud from the ER. These vesicles are call COPII vesicles. However, the machinery (the enzymes that do the modifications in the cis face) are transported BACK from the old cis face (which has now become the medial region of the Golgi) using COPI vesicles (this vesicles type is also used to return material to the ER from the cis), to the new cis face.
The old medial region of the Golgi will transport enzymes back to the new medial, and the old trans face will transport machinery back to the new trans. And the old trans face will break up to give transport vesicles that move on.
That is, it is not the newly manufacteured proteins that is moving through the Golgi, but it is the modification machinery that is moving back.
There is quite a bit of evidence supporting this view. The most compelling evidence is that some proteins that are too big to fit in the COPII and so can't be transported by them through the stack.
