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)  Plant’s have cell walls so they can’t burst, just swell Why grocers spray water on vegetables…to 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.