The Structure of Lipids and Their Biological Functions

The Structure of Lipids and Their Biological Functions

Fats and Oils are substances made up of glycerol and fatty acids and

the only difference between fats and oils is that fats are solid at

room temperature where as oils are not. They both contain atoms of

carbon, hydrogen and oxygen but less oxygen than in a carbohydrate.

The formula for glycerol is C3H8 O3 and the arrangements of the atoms

are shown in the following diagram:

The formula for a fatty acid is much more complex as they vary in size

depending on the lipid it is to be part of.

A Generalised formula for a fatty acid is

The n is decided by the number of carbons attached to two hydrogen's

but n is normally around about 16.

So the above Fatty Acid molecule has the formula

because it has 6 carbons with hydrogen atoms attached to them.

The Carboxyl Group highlighted in pink terminates the molecule and

give it an acidic nature and it is to this end group that bonding

between the glycerol and the fatty acids take place.

Fatty acids and glycerol are the sub-units of a lipid and in the

synthesis of a fat or oil a triglyceride is formed by the combining of

three fatty acids with one glycerol. (Monoglyceride - glycerol and 1

fatty acid, Diglyceride - Glycerol and 2 fatty acids)

The way by which they bond is yet again a condensation reaction which

simply means that water (H20) (in this case three molecules of water)

are removed and an oxygen bond (Ester Bond in this case) is

established.

As I mentioned earlier, some Fatty Acids can have around 16 CH2 bonds.

In some cases not all of the carbon atoms have a hydrogen atom

attached to them and so this type of Fatty Acid is called

"unsaturated" where as if all the bonds are full it is called

"saturated". As carbon atoms must always have four bonds going from

them a double bond is created between two carbon atoms in the chain.