http://iws.collin.edu/biopage/faculty/mcculloch/1406/outlines/chapter%208/8-17.jpg
http://images.tutorvista.com/content/biomembranes/exocytosis-process-in-cell-membrane.jpeg
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/phosphb.htm
http://www.phschool.com/science/biology_place/glossary/wxyz.html#water potential
http://www.phschool.com/science/biology_place/labbench/lab1/watcalc.html