Lipids are composed of hydrogen, oxygen and carbon atoms. They have many purposes and this includes:
- Cell membranes
- Energy sources
- Waterproofing
- Insulation
- Protection
Fatty acids
These lipids are composed of a carboxyl group and a hydrocarbon chain - this is also known as the R group.
The hydrocarbon chain can either saturated or unsaturated.
An unsaturated hydrocarbon chain means that it has at least one double bond - these tend to be liquids at room temperature.
Saturated, on the other hand means that the chain does not contain any double bonds.
Triglycerides
These are fats and oils
A triglyceride is composed of a molecule of glycerol and three fatty acids. They are formed by condensation reaction and are held by an ester bond (-O).
Glycerol is a type of alcohol - one of their hydrogens is lost during the condensation reaction.
Phospholipids
These are used in cell membranes - they form a phospholipid bilayer.
The phosphate head is hydrophilic, polar (like water) and faces outwards. The fatty acid tail is hydrophobic, non-polar (doesn't like water) and therefore they face inwards.
A phospholipid can be formed when one of the fatty acids found in a triglyceride is replaced by a phosphate group.
Other examples
These do not contain any fatty acids:
- Steroids
- Hormones
- Cholesterol