One of several types of biological lipid
molecules. A fat molecule usually contains a glycerol
connected through an ester
linkage to three fatty acid chains (triglyceride
). When these are digested by the body (hydrolyzed
), they break down into glycerol and a fatty acid.
Fatty acids have an even number of carbons in the chains. Some of the chains are all single bonds, therefore called saturated fatty acids. Those with double bonds are known as unsaturated fatty acids. Because addition of a double bond causes a kink in the chain, unsaturated fatty acids dont stack well together and have lower melting points (tend to be liquid at room temperature). Fatty acids that have long chains or are saturated tend to have much higher melting temperatures and will be solid at room temperature. Saturated fatty acids are more unhealthy than unsaturated ones because they are readily converted into the steroid cholesterol, contributing to cardiovascular disease.
Fatty acids act as energy stores and are stored in special cells in the body known as adipose cells. Because triglycerides are not very soluble in water, they tend to pack together, allowing a cell to store large amounts in a small area. Additionally, they are a richer source of energy and one 1g of a triglyceride will usually yield as much energy as two or three grams of carbohydrate.
See also: phospholipid lipid bilayer detergent micelle