BIO206H5 Chapter Notes - Chapter 11: Unsaturated Hydrocarbon, Lipid Bilayer, Membrane Fluidity
Document Summary
Plasma membrane: the thin membrane that surrounds the cell. Can"t be seen directly with a light microscope. Nutrients must pass inward, across the plasma membrane, and waste products must pass out. To facilitate this exchange, the membrane is penetrated by highly selective channels and pumps (protein molecules) Some proteins in the membrane act as sensors that enable the cell to receive information about changes in its environment and respond to them. When a cell grows or changes shape so does its membrane: it enlarges in area by adding new membrane without ever losing its continuity. It can also deform without tearing, and if the membrane is pierced it quickly reseals. All cell membranes are composed of lipids which are arranged in two closely apposed sheets, forming a lipid bilayer. Each lipid has a hydrophilic head and one or two hydrophilic hydrocarbon tails. The most abundant lipids in the cell membrane are phospholipids.
