why is phospholipid very effective as barrier system

watch how phospholipid molecules behave if placed in acqeous solution. Watch formation of fat globules
tell me if you're convinced

http://telstar.ote.cmu.edu/Hughes/tutorial/cellmembranes/orient2.swf

or capy paste this link in your add bar:

http://telstar.ote.cmu.edu/biology/downloads/membranes/