Where do lost membrane proteins go after exocytosis? Exocytotic vesicles take away membrane proteins and glycocalyx on the cell's plasma membrane surface. When those vesicles are released into the interstitial fluid and wherever else, where do they go? Do they stick to the vesicle everywhere? Or do they get removed from the vesicle? If the vesicle fuses into another cell, do those proteins and carbohydrate attachments stick to the new cell?

In the process of exocytosis materials which are about to be released are transported in small vesicles to the plasma membrane. The plasma membrane fuses with these vesicles and this sets the substances free on the outside of the cell. See the figure (from here):!enter image description here

The other possibility for transport vesicles is that they arrive at their target cell and either fuse with the membrane and release the transported substance into the cell or that they are taken up in another vesicle which is then targeted towards the endosome/lysosome. See the figure (from here):

!enter image description here

It doesn't matter which way is chosen, the membrane of the vesicle is recycled either by integration into another membrane of by going through the lysosome.