1. The Plasma Membrane Chapter 7.2

2. Maintaining a Balance  Cells need nutrients like glucose, amino acids, and lipids to function.  The plasma membrane (a.k.a cell membrane) --- acts as a boundary between the cell and its environment.  Allows a steady supply of the nutrients.  Controls the amounts going in and out.  Homeostasis --- maintaining balance

3. Selectively Permeable  Allows some molecules into the cell while keeping others out.  Water freely moves back and forth.  Calcium and salt must also be able to enter into the cell but only at certain times.  So it must be “selective”

4. S tructure  Composed of a phospholipid bilayer --- means phospho (phosphate), lipid (lipid), bilayer (2 layers)  This layering helps the membrane to let certain things in and other not.  Contains transport proteins --- Helps to transport or move certain materials into the cell.