Fatty acids are key components of triglycerides, which we use to store energy in our bodies.
This lesson discusses the important characteristics of these acids in the human body.
What Are Fatty Acids?
A fatty acid is one of the major components of a triglyceride, which is a form of lipid that is used in the body to store energy. A lipid is just a type of molecule that includes, among other things, fatty acids. Triglycerides are a secondary energy source that the body can use in the event that there is not enough sugar (our primary energy source) in the system. While fatty acids vary in terms of chemical characteristics, they all have some basic qualities in common.
Basic Structure of Fatty Acids
Fatty acids are composed largely of a chain of carbon atoms bonded with hydrogen atoms. At one of the terminal ends of a fatty acid is a carboxyl group (-COOH), which is the reactive portion of the molecule and will participate in chemical reactions to make lipids and to store energy. Specifically, this carboxyl group will typically bond with one of the hydroxyl groups (-OH) on a glycerol molecule in a process known as dehydration synthesis.
As this bond forms, energy is stored and water is released as a product of the reaction.Fatty acids vary in terms of the number of carbons that they contain, though it is typically an even number. This chain can be as short as two carbons or as long as necessary for the functions needed, but there will be an even number in the final fatty acid molecule. Since these carbons are located in the chemically inert (non-reactive) part of the molecule, the number of carbons plays a role in the structural characteristics more than in the reactive characteristics.Fatty acids will also vary based on the amount of single and double bonds located in the carbon chain. If a carbon chain has all single bonds, then the molecule is considered to be saturated.
However, if there is at least one double bond between carbon molecules, it is considered unsaturated. Once again, this factor plays a role in the structural characteristics of the molecule, not the reactive.
Saturated vs. Unsaturated Fats
Remember that the carbon chain of the fatty acid will play a role in the structure of the molecule. Saturated fats have carbon chains that are linear, or in a straight line. Unsaturated fatty acids, however, have a kinked (or curved) carbon chain.
This manifests itself in terms of the physical state of the lipid.If carbon chains are linear, then they can stack closely with each other in a manner that will cause them to solidify. Conversely, kinks found in unsaturated fatty acids prevent the molecules from packing tightly and will cause the molecules to form a liquid state.
For us, this means that saturated fats are solid at room temperature. (Think of butter and lard.) However, unsaturated fats, such as your basic cooking oils, will remain liquid at room temperature.
Fatty acids are important molecules for humans because we use them to create lipids, which store energy. Fatty acids may vary in terms of length and structure, but they all have three basic characteristics:
- a carboxyl group for reactions
- an even number of carbons
- either linear or kinked chains
These characteristics will determine what physical state these fats will take and the functions of these molecules in the human body.