In standard lipid shorthand notation, a fatty acid designated as 18:3 contains _____ double bonds in its hydrocarbon chain.

### Why this is right In fatty-acid shorthand, the number before the colon is the number of carbon atoms, and the number after it is the number of double bonds. Thus, 18:3 indicates 18 carbons and three double bonds. ### The concept This compact notation is useful for comparing chain length and unsaturation. It does not specify where the double bonds occur. ### Terms - **Unsaturation**: the presence of one or more carbon-carbon double bonds in a fatty-acid chain. ### Remember The colon separates carbon count from double-bond count.