the plasma membrane is considered
The reason that the cell membrane is considered to be 'semi-permeable' is because there are certain materials that can pass through the cell membrane (e.g. hydrocarbons and oxygen cross through the cell membrane as they can be dissolved into the lipid layer-other examples include small polar molecules.he basic structure of the cell membrane consists of layers. The cell membrane is a phospholid bi-layer. It is made up of proteins and lipids (also known as the phospholipid).