Bonding and properties of triglycerides

Saturated fatty acids

Not only the length of fatty acids can change.

They can also be saturated, with only single bonds between carbon atoms. They contain the maximum number of hydrogen atoms.

Lipids containing only saturated fatty acids generally form fats at room temperature. This is because the fatty acid tails are straight and can pack closely together. Stronger forces of attraction can form which means more energy is needed to break the bonds and melt the fat – the melting point is higher.

Unsaturated fatty acids

Fatty acids can also be unsaturated, with one or more double bonds between carbon atoms.

They do not contain the maximum number of hydrogen atoms. For each carbon-carbon double bond, the fatty acid will contain two fewer hydrogen atoms.

Lipids containing unsaturated fatty acids are usually oils at room temperature.

The double bonds make the fatty acid tails less straight (they kink) so they cannot pack as closely together.

The forces of attraction between the fatty acids are weaker, so less energy is needed to break the bonds and melt the fat – they have a lower melting point.