User:MDougM/Sandbox

The first region on either side of the bilayer is the hydrophilic headgroup. This portion of the membrane is completely hydrated and is typically around 8-9Å thick. In phospholipid bilayers the phosphate group is located within this hydrated region, approximately 5Å outside the hydrophobic core.{{cite journal |title=Structure of lipid bilayers |journal=Biochim. Biophys. Acta |volume=1469 |issue=3 |pages=159–95 |year=2000 |date=November 2000 |last1=Nagle |first1=JF |last2=Tristram-Nagle |pmid=11063882 |first2=S |doi=10.1016/s0304-4157(00)00016-2 |pmc=2747654}} In some cases, the hydrated region can extend much further, for instance in lipids with a large protein or long sugar chain grafted to the head. One common example of such a modification in nature is the lipopolysaccharide coat on a bacterial outer membrane,{{cite book |author=Parker J, Madigan MT, Brock TD, Martinko JM |title=Brock biology of microorganisms|year=2003 |publisher=Prentice Hall |location=Upper Saddle River, NJ }} which helps retain a water layer around the bacterium to prevent dehydration.