3.3-3.5 Cell Boundaries

1. 3.3-3.5 Cell Boundaries

2. Homeostasis • Maintaining an internal balance within our cells! • Body temperature, pH, removal of waste, regulation of water and other substances in our cells. • Cell membranes help control this balance!! • http://www.youtube.com/watch?v=OlHez8gwMgw • http://www.youtube.com/watch?v=d2YWonZsh_M

3. Cell Membrane • Regulates what enters and leaves a cell • Is made from a double layer of lipids (lipid bilayer)

4. Polarity of a phospholipid

5. C. Known as a mosaic because so many things are imbedded in the membrane • Channel Proteins (Doorways) • Protein Pumps • Cholesterol • Places for carbs to attach (cell identifiers)

7. Cell Membranes • They are considered selectively permeable. • Carbon dioxide and oxygen gas can pass right through the cell membrane (non polar molecules) • Charged ions like Na+ and larger molecules like glucose must pass through protein channels/pumps.

8. II. Cell Walls are also porous! A. Provides support and protection for plants, fungus, algae, and some bacteria. • Also porous to allow O2, H2O, CO2, food and waste in and out.

9. III. Diffusion A. Random movement of molecules from where there is a lot (high concentration) to where there is a little (low concentration) – no energy required. example: Ink in water or why your whole house smells like dinner when it’s cooking!

10. This solution is in equilibrium!

11. IV. Facilitated Diffusion • Protein channels/doorways “help” larger molecules in and out of the cell. Ex. Sugar and salt molecules B. Still occurs from high to low concentration and does not require energy.

12. Diffusion vs. Facilitated Diffusion Facilitated diffusion occurs through channel proteins and carrier proteins

14. C. Both diffusion and facilitated diffusion are called passive transportNo energy is needed!

15. Do Now • 1. Distinguish between simple diffusion and facilitated diffusion. • 2. What do diffusion and facilitated diffusion have in common? • 3. How is diffusion related to homeostasis? • Homework: Don’t forget to read 3.4/3.5 and answer the end of section questions in your textbook by tomorrow!

16. V. Active Transport • Molecules are moved in and out of a cell against the concentration gradient. • Requires energy because the molecules are forced to be more crowded

17. small molecules are “pumped” in or out of the cell by the protein pumps in the cell membrane

18. Na+/K+ Pump Responsible for nerve impulses!!

19. VI. Osmosis A. Diffusion of water through a selectively permeable membrane from high to low concentration

20. http://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-181118-5/bm/vadiffus.htmlhttp://www.pearsonsuccessnet.com/snpapp/iText/products/0-13-181118-5/bm/vadiffus.html • animations http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif

21. B. Isotonic solution(equal strength)- When the concentration of water is the same inside and outside the cell

22. C. Hypertonic solution(too strong)– When the water leaves the cell (ex salt on a slug forces water to move out of the slug cells)

23. Red onion cells Add salt water Hypertonic solution Salt pulls water out Cell membrane shrinks

24. D. Hypotonic Solution(under strength) – water moves into a cell because there is not enough inside

26. VII. Osmotic/Turgor Pressure A. Pressure of water inside a cell B. Causes plants to stand up straight C. Can cause cells to burst (cytolysis) D. Cell wall and contractile vacuoles prevent this E. This is how penicillin kills bacteria.

27. VIII. Movement of large molecules 1. Larger molecules that can’t fit in the pumps are moved in and out of the cell with vacuoles • A. Endocytosis – taking molecules in • B. Exocytosis – pushing molecules out

28. 2. 2 kinds of endocytosis a. Phagocytosis – “cell eating” used to take in solids b. Pinocytosis – “to drink” used to take in liquids

29. http://www.youtube.com/watch?v=JShwXBWGMyY&feature=related • http://www.youtube.com/watch?v=K7yku3sa4Y8&feature=related http://www.youtube.com/watch?v=1w10R9lv7eQ