Formation of fats
Most fats exist as triglycerides.
Triglycerides are formed when three fatty acid chains are attached to the glycerol backbone.
Process whereby fatty acids combine with glycerol is known as esterification. Water molecules are formed as a by-product.
Esterification is an example of condensation reaction.
Fig. 19 Structure of a saturated and unsaturated fatty acids. A saturated fatty acid consists of only single bonds between carbon atoms. An unsaturated fatty acid consists of one or more double bonds between carbon atoms.
Fig. 20 Structure of a glycerol molecule.
Fig 21 Structure of a triglyceride molecule.
Types of fats
Depending on the type of fatty acids that bind to the glycerol backbone, fats are classified into two main groups.
1. Saturated fats contain saturated fatty acids that are attached to the glycerol backbone. Ie there are no double bonds between carbon atoms in the fatty acids.
2. Unsaturated fats contain one or more unsaturated fatty acid (ie one or more double bonds between carbon atoms in the fatty acid molecules) molecule(s)attached to the glycerol backbone. Kink(s) in the triglyceride molecule when unsaturated fatty acid molecule(s) is/are attached to the glycerol molecule prevent close packing of the triglyceride molecules à low melting point à exists as liquid oil at room temperature.)
Types of unsaturated fats:
- Classfied based on the number of double bonds in the carbon-carbon chain of fatty acids.
(a) Monounsaturated fats found in peanuts, peanut butter, olives and avocadoes.
(b) Polyunsaturated fats – egs omega-3-fats (soy oils, sardines, mackerel) and omega-6-fats (nuts, seeds, corn oil)