Cell membrane Structure & Function

1. Cell membrane Structure & Function

2. Cell membrane • thin • transparent • porous • flexible • 2-layered • selectively permeable • composed of phospholipids & proteins

3. Cell membrane structure:

4. Transport of molecules through the membrane • Passive Transport – requires no energy A. Diffusion – movement of molecules from an area of high concentration to an area of low concentration ex: osmosis – diffusion of water across a selectively permeable membrane B. Facilitated diffusion – uses transport proteins

5. Transport of molecules through the membrane • Active Transport – requires energy A. Endocytosis – transporting materials into the cell 1.pinocytosis– engulfing small particles or liquids by the cell 2. phagocytosis– engulfing large particles by the cell B. Exocytosis – removing particles using energy

6. 3 solution types • hypertonic – has a greater concentration of solute than inside the cell -causes cell to shrink due to water loss (plasmolysis) • hypotonic – has a lowerconcentration of solute than inside the cell -causes cell to swell due to excess water (cytolysis) 3) isotonic – has the same concentration of solute as inside the cell

8. -An ideal environment for an animal cell is isotonic. -An ideal environment for a plant cell is hypotonic because this provides greater turgor pressure – force exerted by cell wall against the pressure in the vacuole. -When a plant loses turgor pressure, it wilts.