Plasma Membrane Answer these questions 1 What is

Plasma Membrane

Answer these questions: 1. What is a lipid? 2. What does polar mean? What is a polar compound with which you are familiar? 3. Do lipids mix with polar compounds? 4. What does permeable mean? 5. What does it mean to be selective?

Cell Membrane • Sometimes called the plasma membrane • Flexible boundary between the cell and its environment • Selective permeability: permeability some molecules pass through while others don’t – Selectively Permeable • The job of the cell membrane is to maintain homeostasis by letting things in and out of the cell

Cell Membrane • The membrane is made mostly of molecules called phospholipids • These lipids align themselves into two layers • Called the phospholipid bilayer Phospholipid

Cell Membrane • Phospholipids align themselves with their nonpolar “tails” together • This creates a barrier that will keep out most water soluble substances

Fluid Mosaic Model • The name for the model of the membrane because the lipids move within the membrane just as water moves within a current in a lake • There are protein molecules and cholesterol molecules in the membrane as well

Proteins & Cholesterol • Proteins in membrane can serve as transport proteins to move needed substances or wastes through the plasma membrane • Cholesterol stabilizes the plasma membrane by providing support and preventing the fatty acid tails (in phospholipids) from sticking together