Reprinted by permission from Nature
Kiefer et al. Nature 405, 97-101 (2000)

Arachidonate and prostaglandin bound to the cyclooxygenase active site of wild-type COX-2. a, Stereo image of the experimental difference electron density map  before the inclusion of AA (green trace) or PGH2 (gold trace)  b, Diagram of PGH2 (gold) and AA (cyan) bound to the cyclooxygenase active site. Mobile side chains are coloured gold and cyan to match their PGH 2 and AA bound positions, respectively.

Notice the hydrophobic nature of the amino acids surrounding the arachidonic acd.  Note as well the kinks in the arachidonic acid associated with 4 all-cis double bonds in the fatty acid.