Bends in cis Isomers
The best way to demonstrate this kink is with pictures. Usually we have some motivation to try to represent the molecule on a single line. So for oleic acid (cis-octadec-9-en-1-oic acid), we often get pictures like the following:





Elaidic acid, the trans-isomer is also sometimes depicted unhelpfully to save space:





The second structure for elaidic acid is not as misleading as the corresponding structure for oleic acid. A better bond-line structure for oleic acid is:



Better yet, here are some space-filling structures from Wikipedia based on crystal structures of both molecules.

Oleic



Elaidic



And here's $\gamma$-linolenic acid, which has three cis alkenes in it: