Plasma Membrane

Plasma membrane is a thin outer membrane, which maintains
the integrity of the cell. It keeps the cell and its contents
separate and distinct from the surrounding. It is a double
layered measuring about 4.5 nm and made of phospholipids,
cholesterol, glyco-lipid, & carbohydrate (oligosaccharides).
The bi-layer is self-sealing. If a needle is injected and pulled
out, it automatically seals.

Functions: -
1. Separate the cytoplasm inside a cell from extra cellular
fluid.
2. Separate cell from one another
3. Provide an abundant surface on which chemical reaction
can occur.
4. Regulate the passage of materials in to and out of cells. It
also let some things in and keeps others out. The quality
selective permeability

Movement across-cell membrane
Movements a cross membrane takes place in two ways.
These are passive and active movements. Passive movement
uses energy whereas active movement consumes energy in
the form of ATP.