The answer you're looking for is probably two, because a membrane consists of two layers of phospholipids, but it really depends on how the word "layer" is defined in this context.
The plasma membrane is a bi-layer, so two.
plasma membrane and other membranes are the same
They do not have membranes. They are naked organelles
The diffrence is that the cell membrane is just a barrier between the exterior enviroment and the interior of the cell, while the cell surface membrane exerts control over what enters/leaves the cell! :)
Endoplasmic Reticulum
A phospholipid bilayer.
The membrane is continually being lost from the plasma membrane by endocytosis
The membrane is continually being lost from the plasma membrane by endocytosis
Many bacterial plasma membranes do contain a sterol like membrane called hopanoids. Hopanoids are a natural pentacylic compound, this is based on the chemical structure hopane.
Ions can't diffuse across membranes, they must used channels to transport across
Yes, Plasma membrane is present in every living cell.
Yes,all of them have.Every living organism has a plasma membrane.