Known as plasma membrane, forms boundary between cell cytoplasm and environment.
Allows different conditions inside and outside cell and controls movement of substances in and out of cell.
Phospholipids form a bilayer sheet because:
- One layer of phospholipids = hydrophilic heads pointing inwards (water inside cell cytoplasm)
- Other layer has hydrophilic heads pointing outwards (to water outside the cells)
- Hydrophobic tails of both layers point into centre of the membrane, protected from water on both sides.
Lipid soluble material moves through membrane via phospholipid portion. Function of membrane:
- allow lipid-soluble materials in and out.
- prevent water-soluble substances in and out.
- make membrane flexible.
NB: phospholipid has…