7.2 The Plasma Membrane Flexible boundary between cell and its environment. Selective Permeability membrane allows some molecules in, while keeping others out. Think Screen door. Used to maintain homeostasis. 7.2 Plasma Membrane Made up of phospholipids (phosphate group + fatty acid) Bilayer - two layers Arranged tail to tail 7.2 Plasma Membrane The phospholipid Tails are water hating Heads are water loving 7.2 Plasma Membrane Fluid Mosaic Model Fluid lipids and proteins move Mosaic proteins, etc create a pattern LINK 7.2 Plasma Membrane Other players Cholesterol keeps phospholipids from sticking together, keeps it flexible Transport proteins Carbohydrates used like ID tags Glycoproteins protein + sugar Cell Communication Cells most often use chemicals to talk 8.1 Cellular Transport Remember: Diffusion is the movement of particles with a concentration gradient Osmosis- diffusion specifically for water across a selectively permeable membrane. Very important in maintaining homeostasis 8.1 Cellular Transport Isotonic Solution concentration of solute is equal both in and outside the cell There is no net movement 8.1 Cellular Transport Hypotonic Solution concentration of solute outside the cell is lower than inside the cell Water will move into the cell and it will swell (may burst) Plants have cell walls so they cant burst, just swell Why grocers spray water on vegetablesto them look fresh 8.1 Cellular Transport Hypertonic Solution concentration of solute outside the cell is higher than inside the cell. Water will move out of the cell and it will shrink Plant cells cytoplasm pulls away from cell wall and plant wilts. 8.1 Cellular Transport I. Small Particle Transport A. Passive Transport- no E needed, moves with gradient 1. Simple Diffusion 2. Facilitated Diffusion uses transport proteins a. Channel Proteins - pathway b. Carrier Proteins change shape 8.1 Cellular Transport B. Active Transport requires energy, moves against gradient 1. Carrier Proteins fits specific molecules, change of shape (open to inside) needs E. 8.1 Cellular Transport II. Large Particle Transport A. Endocytosis cell engulfs mass with PM PM breaks off to become a vacuole inside cell student.ccbcmd.edu/.../images/phagocyt.gif 8.1 Cellular Transport B. Exocytosis Vacuole with waste, hormones, etc merges with PM Contents are release outside the cell.