fatty acid
Meaning of fatty acid: The chemical building block of fats, and the reason one fat behaves so differently from another.
Definition of fatty acid
A fatty acid is a chain of carbon atoms carrying an acid group at one end, and it is the building block from which nearly all fats and oils are made. Fatty acids supply energy, are stored in fat tissue when they are not needed, and form the membranes that enclose every cell. The length and shape of the chain determine how a fat behaves.
What makes one fatty acid different from another?
Two features do most of the work: how long the carbon chain is, and whether it contains any double bonds. A double bond puts a kink in the chain, so the molecules cannot pack together tightly, and the fat stays liquid at room temperature.
| Type | Double bonds | Usually found in |
|---|---|---|
| Saturated | None | Butter, lard, coconut oil; solid when cool |
| Monounsaturated | One | Olive oil, avocado |
| Polyunsaturated | Two or more | Fish, walnuts, sunflower oil |
| Trans | One or more, straightened | Some processed and fried foods |
What does the body do with them?
Fatty acids are broken apart two carbons at a time to release energy, a process that yields more energy per gram than sugar does. What is surplus is joined onto a glycerol backbone and stored as triglyceride in fat tissue. A separate share is never burned at all: it is built into cell membranes, and a further portion is converted into signaling molecules that govern inflammation and blood clotting.
What does essential mean here?
The body can manufacture most fatty acids it needs from other raw materials. Two families cannot be made and have to come from food, which is why they are called essential. These are the omega-3 and omega-6 groups, both of them polyunsaturated. The number in omega-3 simply records where the first double bond sits, counting from the tail end of the chain.
Used in a sentence
Laboratory analysis measured the fatty acid composition of the membrane samples.
Good to know
Saturated and unsaturated describe chemical structure, not nutritional value, and the two essential families are the omega-3 and omega-6 groups.