Fatty acid
Say it: FAT-ee AS-id
A fatty acid is a long chain of carbon and hydrogen atoms with a carboxyl group at one end, and is the building block of fats, oils and phospholipids.
Also: fatty acids
Definition
What is a fatty acid?
A fatty acid is a hydrocarbon chain, a backbone of carbon atoms carrying hydrogen atoms, that ends in a carboxyl group (COOH), the acidic part that gives the molecule its name. Chains in living things range from about 4 to 36 carbons, and most have 12 to 18. Three fatty acids attached to glycerol make a triglyceride, the main form of stored fat, and two attached to a glycerol phosphate make a phospholipid.
Fatty acids are classed by their bonds. Saturated fatty acids have only single bonds between carbons, so their straight chains pack tightly, and fats rich in them, such as butter, are solid at room temperature. Unsaturated fatty acids have one double bond (monounsaturated) or more (polyunsaturated); a cis double bond puts a kink in the chain, which keeps oils liquid. Partly hydrogenating oils can create trans fatty acids, which are linked to raised LDL cholesterol.
The body cannot make omega-3 and omega-6 fatty acids, so they are essential in the diet; oily fish, walnuts and flaxseed are rich sources of omega-3s. When energy is needed, cells break fatty acids down by beta-oxidation, feeding the citric acid cycle.
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Terms that go with it
- LipidA lipid is one of a varied group of biological molecules, including fats, oils, phospholipids, waxes and steroids, that do not dissolve in water.
- CholesterolCholesterol is a waxy steroid lipid found in animal cell membranes and used to make steroid hormones, vitamin D and the bile salts that digest fat.
- Citric acid cycleThe citric acid cycle is a loop of reactions in mitochondria that breaks down acetyl groups to carbon dioxide, capturing energy as NADH and FADH2.
- Cell membraneThe cell membrane is the thin, flexible boundary of lipids and proteins that encloses every cell and controls what enters and leaves it.
- MacronutrientA macronutrient is a nutrient needed in large amounts, namely carbohydrate, protein or fat, which together supply energy and the raw materials for growth.
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Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 3.3 Lipids
- MedlinePlus: Facts about polyunsaturated fats
- MedlinePlus: Facts about saturated fats
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