Fatty acids

Saturated: they only have single bonds between carbons.
General formula:

H-(CH₂)_n-COOH

Example: palmitic acid, with 16 carbon atoms (16:0).
This is its most extended conformation, although the hydrocarbon chain is flexible and can bend. Check out the end view:

Unsaturated: they have double bonds, that force the chain to bend. Examples:

Oleic acid, with 18 carbon atoms and a double bond betwwen carbons 9 and 10 (18:1 Delta ⁹).
the CH-CH double bond.
double bonds as double sticks.

You may get a .
Observe that the two carbons and the four atoms linked to them lay all in the same .
Furthermore, the bond is rigid, does not allow rotation, in contrast to single CH₂-CH₂ bonds. This is important for the structure of the fatty acid and its properties, such as melting point.

Linoleic acid, with 18 carbon atoms and 2 double bonds, between carbons 9-10 and betwwen 12-13 (18:2 Delta

^9,12).

the CH-CH double bonds.
double bonds as double sticks.

Linolenic acid, with 18 carbon atoms and 3 double bonds, between carbons 9-10, 12-13, and 15-16 (18:3 Delta

^9,12,15).

the CH-CH double bonds.
double bonds as double sticks.