Membrane Structure and Function. Chapter 7. Plasma membrane of cell selectively permeable ( allows some substances to cross more easily than others) Made mostly of proteins and lipids (phospholipids). Phospholipids and proteins create unique physical environment (fluid mosaic model).
http://faculty.southwest.tn.edu/jiwilliams/plasmolysis.gif from cell (plasmolysis).
In this case, the protein actually rotates ] gradient with help of transport protein.
to dump the materials to the inside
of the cell.