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The Cell Membrane and Movements of Molecules The Plasma Membrane The Plasma Membrane (aka cell membrane) The Plasma Membrane (aka cell membrane) Boundary.

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Presentation on theme: "The Cell Membrane and Movements of Molecules The Plasma Membrane The Plasma Membrane (aka cell membrane) The Plasma Membrane (aka cell membrane) Boundary."— Presentation transcript:

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2 The Cell Membrane and Movements of Molecules

3 The Plasma Membrane The Plasma Membrane (aka cell membrane) The Plasma Membrane (aka cell membrane) Boundary between the cell and its environment Boundary between the cell and its environment Controls what enters and leaves the cell--- performing homeostasis Controls what enters and leaves the cell--- performing homeostasis Has selective permeability- the ability to allow some molecules through the membrane -but not others (aka semi-permeability) Has selective permeability- the ability to allow some molecules through the membrane -but not others (aka semi-permeability)

4 Water Plasma Membrane

5 Plasma Membrane Structure

6 Fluid Mosaic Model describes the structure of the plasma membrane describes the structure of the plasma membrane Fluid: Phospholipids Fluid: Phospholipids Polar head- loves water Polar head- loves water 2 Fatty acid tails- avoid water 2 Fatty acid tails- avoid water

7 Fluid Mosaic Model Phospholipids in water form a double layer sandwich with tails pointing in Phospholipids in water form a double layer sandwich with tails pointing in

8 Fluid Mosaic Model The sandwich forms a hollow sphere with an inside and an outside The sandwich forms a hollow sphere with an inside and an outside

9 Fluid Mosaic Model The phospholipids are considered fluid because they can move throughout the membrane. The phospholipids are considered fluid because they can move throughout the membrane.

10 Fluid Mosaic Model Mosaic: Proteins Mosaic: Proteins embedded in the phospholipid bilayer embedded in the phospholipid bilayer

11 Fluid Mosaic Model 3 types of proteins: 3 types of proteins: Transport proteins-allow molecules to enter or leaveTransport proteins-allow molecules to enter or leave Support proteinsSupport proteins Recognition proteinsRecognition proteins

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13 Other Membrane Structures Cholesterol- makes the membrane less permeable Cholesterol- makes the membrane less permeable

14 Other Membrane Structures Carbohydrate Chains-glycoproteins allow cells to recognize each other. Carbohydrate Chains-glycoproteins allow cells to recognize each other. Immune system Immune system

15 COLOR AND LABEL THE MEMBRANE STRUCTURES

16 Molecular Movements Molecules of liquids and gases are in constant random motion Molecules of liquids and gases are in constant random motion –Travel in a straight line path –Bump into another molecule –Bounce off on another straight line course

17 Molecular Movements Diffusion-net movement of the same kind of molecule Diffusion-net movement of the same kind of molecule From an area of high concentration to an area of low concentration- aka down a concentration gradient From an area of high concentration to an area of low concentration- aka down a concentration gradient Continues until the molecules are equally distributed Continues until the molecules are equally distributed

18 Molecular Movements Osmosis –the diffusion of water through a selectively permeable membrane Osmosis –the diffusion of water through a selectively permeable membrane From an area of high concentration to an area of low concentration- aka down a concentration gradient From an area of high concentration to an area of low concentration- aka down a concentration gradient

19 Osmosis The concentration of water in solution increases as the concentration of solutes decreases The concentration of water in solution increases as the concentration of solutes decreases 5% salt solution means ?% water5% salt solution means ?% water 5% salt solution means 95% water5% salt solution means 95% water 10% salt solution means ?% water10% salt solution means ?% water 10% salt solution means 90% water10% salt solution means 90% water

20 20% Solute 80% Solute Which direction will the water flow? -Towards side A Or -Towards side B AB

21 Types of Solutions Isotonic Solution: Concentration of solutes is the same inside and outside the cell. Isotonic Solution: Concentration of solutes is the same inside and outside the cell. Some water moves in, some water moves out. Some water moves in, some water moves out. No net movement of water. No net movement of water. Cell remains the same. Cell remains the same.

22 Types of Solutions Isotonic Solution: Isotonic Solution:

23 Hypotonic Solution: The concentration of solutes is less outside the cell than inside the cell. Hypotonic Solution: The concentration of solutes is less outside the cell than inside the cell. Net movement of water into the cell. Net movement of water into the cell. The cell will swell and may burst. The cell will swell and may burst. Ex: distilled water, pure water, pond water Ex: distilled water, pure water, pond water Types of Solutions

24 Hypotonic Solution: Hypotonic Solution: Types of Solutions

25 Hypertonic Solution: The concentration of solutes is more outside the cell than inside the cell. Hypertonic Solution: The concentration of solutes is more outside the cell than inside the cell. Net movement of water out of the cell. Net movement of water out of the cell. Cell will shrink. Cell will shrink. Ex: salt water, sea water, ocean water Ex: salt water, sea water, ocean water Salt sucks!

26 Types of Solutions Hypertonic Solution: Hypertonic Solution: osmosis

27 Comparison of Hypo, Iso, and Hypertonic Solutions

28 88% H 2 O 99% H 2 O Which direction will the water flow? Water always flows from high to low Water (H 2 O)

29 25% H 2 O 10% NaCl Which direction will the water flow? Change % NaCl to % water –osmosis is the movement of water through the plasma membrane 90% H 2 O Water (H 2 O)

30 90% H 2 O 80% H 2 O Which direction will the water flow? Water always flows from high to low Water (H 2 O)

31 Osmotic Pressure in Plant Cells Turgor Pressure: The pressure in a plant cell that results from water flowing into the cell- maintaining central vacuole. Turgor Pressure: The pressure in a plant cell that results from water flowing into the cell- maintaining central vacuole. Gives plants the ability to stand up. Gives plants the ability to stand up.

32 Osmotic Pressure in Plant Cells With loss of turgor pressure central vacuole shrinks--plants wilt! With loss of turgor pressure central vacuole shrinks--plants wilt! Plant cells require hypotonic situation to maintain turgor pressure Plant cells require hypotonic situation to maintain turgor pressure


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