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7-3 Cell Boundaries

7-3 Cell Boundaries. Cell Membrane. The cell membrane regulates what enters and leaves the cell and also provides protection and support. The composition of nearly all cell membranes is a double- layered sheet calles a lipid bilayer.

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7-3 Cell Boundaries

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  1. 7-3 Cell Boundaries

  2. Cell Membrane The cell membrane regulates what enters and leaves the cell and also provides protection and support. The composition of nearly all cell membranes is a double- layered sheet calles a lipid bilayer.

  3. The cell membrane regulates what enters and leaves the cell and also provides protection and suport. Lipid Bilayer- A membrane with a doble- layer

  4. Cell Walls • The main function of the cell wall is to provide support and protection of the cell.

  5. Cytoplasm – Contains a solution of many different substances in water. Solution- A mixture of two or more substances. Solute – Substances dissolved in the solution.

  6. Concentration – A solution is the mass of solute in a given volume of solution.Mass/ Volume 12 Grams of salt 3 Lt. Water 12 Grams of Salt 6 Lt. of Water What solution has the most concentration?

  7. Concentration 12 g./6L or 2g/L 12 g./ 3 L. or 4 g/L The first solution is twice as concentrated as the second solution.

  8. More concentration If you dissolved 12 grams of salt in 3 liters of water, what is the concentration for salt in the solution?

  9. Suppose you added 12 more grams of salt to the solution. What would be the resulting concentration?

  10. What if you then added another 3 liters of water to that solution concentration?

  11. Which solution of the ones discussed would be called the most concentrated?

  12. Diffusion • Particles move constantly. The particles tend to move from an area where they are more concentrated to an area where they are less concentrated.

  13. Equilibrium- when the concentration of the solute is the same throughout a system. Diffusion depends upon random particle movemnts, substances diffuse across membranes without requiring the cell to use energy.

  14. Osmosis • Is the diffusion of water through a selectively permeable membrane.

  15. Permeable Some substances can pass across then and others cannot.

  16. Isotonic- The concentration of solutes is the same inside and outside. “Same Strength” Hypertonic – Solution has a higher solute concentration than the cell. “Above Strength” Hypotonic – Solution has a lower solute concentration than the cell. “Below Strength”

  17. Watch this for a better explanation on hypertonic and hypotonic http://www.youtube.com/watch?v=DpVbcJY4amA http://www.youtube.com/watch?v=1vQzqk2hzj8&feature=related

  18. Gather your thoughts • In the beaker on the left, which solution is hypertonic and which is hypotonic? Pg. 185 • In this model, to which material is the membrane permeable, water or sugar?

  19. Visual Activity www.phschool.com Code: cbp-3075

  20. Osmotic pressure For organisms to survive, they must have a way to balance the intake ans loss of water. Cells in large organisms are not in danger of bursting. Plant cells and bacteria are surrounded by tough cel walls. The cell walls prevent the cells from expanding even under tremendous osmotic pressure.

  21. Facilitated Diffusion Cell membranes have protein channels that make it easy for certain molecules to cross the membrane. Cell membrane protein facilitate the diffusion of glucose, or other substances across the membrane. The net movement of molecules across a cell membrane will occur only if there is a higher concentration of the particular molecules on one side than on the other side. No energy is required.

  22. Active Transport Sometimes it must move materials in the opposite direction, against concentracion difference. It requires energy. It can be by transport proteins or “pumps” that are found in the membrane. Larger molecules can be processes by endocytosis and exocytosis.

  23. Endocytosis The process of taking material into the cell by means of infolding of the cell membrane. The poket that results breaks loose from the outer portion of the cell membrane and forms a vauole

  24. Phagocytosis The cell engulfs particle and package it within a food vacuole.

  25. Pinocytosis Cells take up liquid form the surrounding enviroment by introducing valuoles of water.

  26. The release of large amounts of material from the cell. The membrane of the vacuole surrounding the material fuses with the cell membrane forcing the contents out of the cell.

  27. Quick Lab • How can you model permeability in cells? Materials: graduated cylinder, plastic sandwich bag, starch, twist tie, 500 ml beaker, iodine solution Procedure: 1- Pour about 50 ml of water into a plastic sandwich bag. Add 10 ml of starch. Secure the bag with a twist tie, and shake it gently to mix in the starch.

  28. 2- Put on your goggles, plastic gloves and apron. 3- Pour 250 ml of water into a 500 mL beaker. 4- Place the sandwich bag of water and starch into the beaker of water and iodine. 5- After 20 minutes, look at the sandwich bag in the beaker. Observe and record any changes that occurred.

  29. http://staff.tuhsd.k12.az.us/gfoster/standard/bcell1.htm http://io.uwinnipeg.ca/~simmons/cm1503/membranefunction.htm

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