Vesicles and cell wall and membranes?

Question

If vesicles transport material for the construction of cell walls, and deposit it by fusing with the plasma membrane, then do plasma membranes grow with time (due to the fusing of secretory vesicles), or does it too decompose into vesicles?

Answer 1

Just as there is vesicular fusion with the cell membrane, there is also endocytosis, which derives vesicles from the membrane where they traffic within the cell.  Furthermore, cell membranes undergo a process of membrane recycling, where older phospholipids (which are susceptible to oxidation) are replaced by newly synthesized ones.  So there needs to be a balance between constituents added to the membrane and removed from the membrane to maintain cell size.

With this said, some cells do grow in size.  One cell type that I can think of are macrophages.  These are immune cells that can get pretty big when they are activated.  But this is due to specific stimuli, rather than just a generalized thing that they do as they age.