The cell membrane is formed by a bilayer of phospholipids and proteins. The phospholipids form a stable barrier between the inside and outside of the cell because they have the property of being poorly soluble in water.
The cellular membrane and its proteins are assembled in the endoplasmic reticulum known as ER. This organelle contains enzymes that are involved in lipid synthesis.
After being siynthesized they are transported to the Golgi apparatus that has the function of assembling the membrane proteins.
Vesicular transport is used to exchange proteins and lipids between the ER and the Golgi apparatus and then direct the final components of the cell membrane to the proper destinations