Diffusion, Osmosis, and Cellular Transport

1. Diffusion, Osmosis, and Cellular Transport

2. Movement of Particles Atoms and molecules collide causing them to move around randomly Causes diffusion

3. Diffusion • When molecules move from an area of high concentration to low concentration • No energy required • http://www.biologycorner.com/bio1/diffusion.html

4. Dynamic Equilibrium Diffused particles eventually reach a dynamic equilibrium Dynamic= changing, moving Equilibrium = balanced Molecules will continue to move but no overall concentration change http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html

5. Cell Membrane • Maintains homeostasis (balance) by controlling what comes in and what goes out • Semi-permeable- some substances can pass freely in and out of the cell while others do not

6. Cell Membrane cont. Made of a phospholipidbilayer And proteins (2 types) Transport proteins- move substances across membrane Signal proteins- communicate with other cells

7. Diffusion into Cells • Particles that are small and have no charge can get into the cell by diffusing directly through the membrane (between phospholipids) • CO2, O2, H2O • Large particles (like glucose) must enter and exit through a membrane protein in a process called facilitated diffusion • It’s still diffusion, so no energy needed • The diffusion of water has a special name called osmosis • Again, it’s a type of diffusion so no energy needed

8. Facilitated Diffusion Large molecules moving with the concentration gradient (high to low) use a protein to facilitate (help) their crossing the cell membrane Diffusion = no energy!

9. Osmosis The diffusion of water Water moves from high concentration to low concentration across the cell membrane http://www.biologycorner.com/bio1/diffusion.html Water concentration is affected by the amount of solute dissolved in the water

10. Osmosis in Cells Water moves either in or out of the cell depending on the concentration of water inside and outside the cell Hypotonicsolution- water concentration greater outside the cell Water moves into the cell Hypertonic solution- water concentration less outside the cell Water moves out of the cell Isotonic solution- water concentration the same both in and out of the cell Same amount of water moves in and out of the cell

12. Passive Transport Diffusion, facilitated diffusion and osmosis are all forms of passive transport because each moves substances in and out of the cell without any energy input by the cell

13. Active Transport • Substances are moved in and out of the cell against the concentration gradient (from low concentration to high concentration) • Requires energy