Diffusion and Osmosis: How does stuff get into and out of a cell?

1. Diffusion and Osmosis: How does stuff get into and out of a cell? The Cell in its Environment

2. Molecules are always moving • Molecules move randomly and bump into each other and other barriers

3. Diffusion • Movement of molecules from an area of high concentration to an area of lower concentration • Continues until equilibrium is reached.

4. Diffusion

5. Diffusion • When diffusion occurs without control or energy use it is called Passive Transport • Affected by: • Size of molecules • Size of pores in a membrane • Temperature • Stirring

7. Simple Diffusion

8. Cell Membranes are Semipermeable • Let some molecules pass through and not others. • Small molecules pass through – ex: water • Large molecules can’t pass through – ex: proteins and complex carbohydrates

10. Which molecules will diffuse? 1 2 3 4 5 6

11. How long does diffusion continue? • Until equilibrium is reached: Equilibrium - means there will be an equal distribution of molecules throughout the space – this is why odors smell strong at first, then seem to disappear

12. Osmosis – A Special kind of Diffusion • Diffusion of water across a selectively permeable membrane • Cytoplasm is a solution of water and solutes(stuff dissolved in the water). • Water moves into and out of cells because of the different concentrations of the solutes. • Different kinds of cells react differently to osmosis, depending on the solution they are in:

13. Type of Solution • Hypertonic – a solution that has a higher concentration of solute outside of the cell than inside. Water moves out of the cell and shrinks it. • Hypotonic – a solution that has a higher concentration of a solute inside the cell than outside. Water moves into the cell and expands it. • Isotonic – a solution that has an equal concentration of a solute inside the cell as outside the cell. Water and solute is equalized.

15. Blood in different solutions:

16. Active Transport – uses carrier molecules to move molecules from an area of lower concentration to an area of higher concentration

17. Endocytosis • Very large molecules or substances must enter the cell by the membrane pinching inward:

18. Pinocytosis • The cell takes in liquid droplets and forms a vacuole

19. Phagocytosis • The cell takes in large particles

20. Exocytosis • The cell gets rid of secretions or wastes

21. Phagocytosis in action – phagocyte (white blood cell) going after a bacteria cell The End

22. Diffusion and Osmosis Video Clip https://www.teachertube.com/video/diffusion-and-osmosis-2-347195