It is because of the unique properties of the phospholipid bilayer that vesicles are able to so easily fuse with the Golgi apparatus and the plasma membrane, If not for these properties the endomembrane system would not function.
The structures (organelles) that make up the endomembrane system are: The nuclear envelope, The rough and smooth ER, the Golgi apparatus and Golgi bodies, lysosomes, various vesicles, and the plasma membrane.
The nuclear envelope (found around the nucleus) is made of a double phospholipid bilayer, it has two double layers of phospholipids and many pores. The Nuclear envelope separates the contents of the nucleus from the cytoplasm while still allowing the nucleus and the cytoplasm to communicate the nuclear pores allow mRNA and ribosomal subunits out of the nucleus and protiens into the nucleus The outermost membrane is continuous with the rough ER and has ribosomes its function is similar to that of the plasma membrane.
The endoplasmic reticulum extends out form the nuclear envelope it too is made of a phospholipid bilayer. It weaves through the cytoplasm like hollow canals. The rough ER is studded with ribosomes it functions to fold, transport, and wrap proteins in a membranous sac forming a vesicle that can then transport the protein to its destination. The smooth ER is continuos with the rough ER and has no ribosomes it makes lipids and or steroid and vesicles its specific function changes depending on what type of cell it is in.
Vesicles have many different functions and types they participate in exocytosis, pinocytosis, and...