Fatty Acids
Definition and meaning of Fatty Acids in chemistry.
Fatty acids are long chains of carbon and hydrogen atoms ending in an acid group called -COOH. Most natural fatty acids have between 4 and 28 carbon atoms in an unbranched chain. They are the basic building blocks of fats and cell membranes.
In more detail
Fatty acids come in two main types. Saturated fatty acids have only single bonds between their carbon atoms, so the chain lies straight. Unsaturated fatty acids have one or more carbon-carbon double bonds, which usually bend the chain at each double bond.
Straight, saturated chains pack together tightly, which is why fats like butter stay solid at room temperature. Bent, unsaturated chains cannot pack as closely, so oils like olive oil stay liquid. In your body, three fatty acids attach to a small molecule called glycerol to form a triglyceride, the main way your body stores extra energy.
When two fatty acids and a phosphate group attach to glycerol instead, the result is a phospholipid, the main building block of every cell membrane. Not every unsaturated fat is automatically healthier than a saturated one. Trans fats, an unusual unsaturated type, are actually linked to heart disease.
Some fatty acids, called essential fatty acids, cannot be made by the human body at all and must come from food. Chain length also affects how fats behave. Short-chain and medium-chain fatty acids, found in foods like coconut oil, are digested and absorbed differently than the longer-chain fatty acids typical of most other fats.
Fatty acids also help form the flexible tails on soap and surfactant molecules used in everyday cleaning products.
Key facts
| Field | Biochemistry |
|---|---|
| General formula | CH3(CH2)nCOOH |
| Functional group | Carboxylic acid (-COOH) |
| Example | Oleic acid, C18H34O2 |
| Stored form | Triglycerides (3 fatty acids plus glycerol) |
| Membrane form | Phospholipids (2 fatty acids, phosphate, plus glycerol) |
Oleic acid is a common fatty acid found in olive oil. Its formula is CH3(CH2)7CH=CH(CH2)7COOH. It has one carbon-carbon double bond, which makes it monounsaturated and gives olive oil its liquid texture at room temperature.
Frequently asked questions
What is the difference between saturated and unsaturated fatty acids?
Saturated fatty acids have only single bonds between carbon atoms. Unsaturated fatty acids have one or more carbon-carbon double bonds, which are usually in the cis shape in natural fats.
What are essential fatty acids?
Essential fatty acids, such as linoleic acid and alpha-linolenic acid, cannot be made by the human body and must come from food.
Are unsaturated fats always healthier than saturated fats?
Not always. Most natural unsaturated fats are considered healthier in moderation, but trans fats, an unnatural unsaturated type made during partial hydrogenation, are linked to heart disease.