Scientists Say: Fatty acid

These tiny chains make up cell membranes, and keep you going when sugar runs out

fatty acids

These are examples of fatty acids. They all have long chains of carbon (black) with hydrogens on the outside (gray) in common.

(Automated conversion) at English Wikipedia (Transferred from en.wikipedia to Commons.) [GFDL ( or CC-BY-SA-3.0 (], via Wikimedia Commons

Fatty acid (noun, “FAT-ee acid”)

A fatty acid is a common kind of molecule in living things. All fatty acids have a similar structure: At the core is a long chain of carbon atoms linked together. The carbons have hydrogens bonded on their outsides. At one end, the chain is linked to a carboxylic acid. That’s a quartet of one carbon, two oxygens and a hydrogen, grouped together.

When two fatty-acid chains pair up with a phosphate group (a phosphorous atom surrounded by oxygen atoms) at their head, they form a phospholipid. The phosphate end loves water. The fatty acid end does not. To protect themselves in a liquid environment, groups of phospholipids will self-organize. The water-loving ends point out toward water, while the water-hating ends pair with each other. A double layer of phospholipids forms something important — a membrane. Every single cell in your body is surrounded by one.

If three fatty-acid chains get together, another structure can link them. It is a glycerol (a very short three-carbon chain). And this forms a triglyceride. These molecules are the building blocks of body fat. The body can quickly break down this body fat for energy when no food is available, protecting us from starvation.

In a sentence

Bacteria in the gut release fatty acids, and one of them — called priopionate — may help people eat less.

Follow Eureka! Lab on Twitter

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

More Stories from Science News Explores on Chemistry