Lipid Bilayers: Basis of Cell Membranes
- Phospholipids form the basic structure of cell membranes, which are formed from phospholipid bilayers
- They are formed by a hydrophilic phosphate head bonding with two hydrophobic hydrocarbon (fatty acid) tails
- As phospholipids have a hydrophobic and hydrophilic part they are known as amphipathic
- The phosphate head of a phospholipid is polar and therefore soluble in water (hydrophilic)
- The fatty acid tail of a phospholipid is nonpolar and therefore insoluble in water (hydrophobic)
Phospholipid structure diagram
Phospholipids consist of a molecule of glycerol, two fatty acid tails, and a phosphate group
- When phospholipids are placed in water the hydrophilic phosphate heads orient towards the water and the hydrophobic hydrocarbon tails orient away from the water
- This forms a phospholipid monolayer
Phospholipid monolayer diagram
Phospholipids can form a monolayer in water
- When there is a sufficient concentration of phospholipids present then two-layered structures may form
- These sheets are called phospholipid bilayers
Phospholipid bilayer diagram
A phospholipid bilayer is composed of two layers of phospholipids; their hydrophobic tails facing inwards and hydrophilic heads outwards