The Plasma Membrane
The plasma membrane is a semi-permeable lipid bilayer found in all cells that controls water and certain substances in and out of the cell.Function of the Plasma Membrane
- Protects the cell.
- Separates the intracellular components from the extracellular environment.
- Controls what enters and exits the cell
Necessities for the Movement of Substances across the Plasma Membrane
- To transport nutrients into the cell.
- For gases exchange
- To excrete metabolic waste.
- To maintain the pH value and ionic concentration of the cell.
Substances In and Out through the Membrane
![](http://spmbiology.blog.onlinetuition.com.my/wp-content/uploads/sites/20/2014/05/substancesinandout.png)
Structure of the Plasma Membrane
Fluid Mosaic Model
Internet Resources (Flash Animation)
Permeability of the Phospholipids Bilayer
The permeability of the phospholipids bilayer is determined by:- the size
- the charge and
- the polarity
![](http://www.one-school.net/Malaysia/UniversityandCollege/SPM/revisioncard/biology/movementacrossmembrane/images/permeability.png)