A fatty acid is a simple lipid, or fat, that is classified according to the number of carbons and the number of double bonds it possesses. Polyunsaturated fatty acids are a type of fatty acid that contain two or more carbon-carbon double bonds. Removal of hydrogen pairs make this possible.
Structure
Polyunsaturated fatty acids are composed of a straight chain of carbons and hydrogens. The length can vary from four to 24 carbons, and there may be as many as six carbon-carbon double bonds in the molecule. The chain terminates with a carboxylic acid group, creating a water-soluble and water-insoluble end. Often, these fatty acids have kinks or bends in their structure.
Function and Characteristics
Polyunsaturated fatty acids are essential for proper membrane function. Due to the presence of kinks and bends, polyunsaturated fatty acids can pack more loosely, making the cell membrane less stiff and rigid. This is critical for the membrane's fluidity and permeability, which affects the activity of proteins embedded in it. In addition, polyunsaturated fatty acids are usually liquid at room temperature, and they are rarely free in nature. Instead, they are usually attached to other molecules, like phospholipids or triglycerides, at their carboxylic acid end.
Food Sources
You'll find some of the common polyunsaturated fatty acids in various vegetable and marine oils, including soybean, corn, canola, safflower, cottonseed, sunflower seed, flaxseed, peanut and fish oil. Some leafy vegetables also contain these fatty acids.
Health Claims
The most well-known polyunsaturated fatty acids are omega-3 and omega-6. Omega-3s, especially, have sparked much nutritional interest due to claims that these polyunsaturated fatty acids lower blood pressure, significantly reduce blood triglyceride levels and prevent heart disease, notes MayoClinic.com. There is also some evidence it may aid rheumatoid arthritis and play in role in cancer prevention. Fish oils are a particularly good source of the omega-3 fatty acids.
References
- "Advanced Nutrition and Human Metabolism"; Sareen Gropper, Jack Smith, and James Groff; 2009
- "Krause's Food, Nutrition, & Diet Therapy"; L. Kathleen Mahan and Sylvia Escott-Stump; 2004
- MayoClinic.com: Omega-3 Fatty Acids, Fish Oil, Alpha-Linolenic Acid
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