1. Membranes organize a cell’s activities Ch. 6.2

2. ► Plasma membrane acts as a cell’s boundary ► Regulates the traffic of chemicals that go in and out of the cell

3. Membrane Structure ► Acts as a partition ► Allows certain substances to pass in and out to the cell

4. ► Made of proteins and lipids  PHOSPHOLIPID  2 fatty acids ► The tail is HYDROPHOBIC ► The head is HYDROPHILIC ► Also includes a phosphate (PO 4 -3 ) group

6. ► Helps form boundaries btwn 2 watery environments  Separates cytoplasm from the surrounding of a cell ► Sandwich of the phospholipids called a PHOSPHOLIPID BILAYER

7. The Many Functions of Membrane Proteins ► Proteins perform most of the membrane’s functions  Helps carry out chem. rxns  Helps cells communicate and recognize each other  Helps move substances across the membrane in and out of the cell

8. Concept Check ► Describe how phospholipid molecules are oriented in the plasma membrane of a cell. ► What is the function of a transport protein?