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Cell Structure & Function

Cell Structure & Function. Structure & Movement Through Membranes (There and Back Again). The Cell Membrane. Key Concept: The cell membrane regulates what enters and leaves the cell and also provides protection and support. The Cell Membrane.

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Cell Structure & Function

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  1. Cell Structure & Function Structure & Movement Through Membranes (There and Back Again)

  2. The Cell Membrane Key Concept: The cell membrane regulates what enters and leaves the cell and also provides protection and support

  3. The Cell Membrane • The cell takes in nutrients and expels wastes plus cell products through the cell membrane • The Basic Structure Of Nearly All Cell Membranes Is The LIPID BILAYER

  4. LIPID BILAYERS • Form Automatically When Certain Lipids Are Dissolved In Water • Tough Flexible Structure • Strong Barrier Between Cell Contents And Its Surroundings

  5. LIPID BILAYERS

  6. LIPID BILAYERS

  7. Fluid Mosaic Model In Addition To The Bilayer,The Cell Membrane Contains: • Proteins That Form • Channels & Pumps • Proteins with Carbohydrates That Form • Antigenic Sites • Communication Sites

  8. Diffusion All Living Cells Contain And Are Surrounded By Liquid. • THE CELL MEMBRANE REGULATES THE MOVEMENT OF MOLECULES FROM ONE SIDE OF THE MEMBRANE TO THE OTHER

  9. Cytoplasm Is A SolutionOf Many Different Substances In Water

  10. Solution A liquid mixture of 2 or more substances evenly mixed. • Solvent • The liquid in which the substances are mixed • Solute • Substances dissolved in the Solvent

  11. Concentration Of Solution Concentration = Mass of the solute in a given volume of solvent. Mass/Volumee.g. 12g of NaCl dissolved in 3L H2O equals 12g/3Lor4.0 g/L

  12. In A Solution Molecules Are Moving Constantly They Collide and Bounce off each other This causes them to spread out randomly Resulting In: Movement from:an area of higher concentration to an area of lower concentrationThis process is called: Diffusion

  13. DIFFUSION • Molecules move awayfrom an area of Higher Concentration to area’s of Lower Concentration • Equilibrium • Concentration of a solute is the same throughout the solution • The concentration is the same EVERYWHERE

  14. Diffusion

  15. DIFFUSION Key Concept:Diffusion Causes Many Substances To Move Across A Cell Membrane But: Diffusion Does NOTRequire The Cell To Use EnergyIt just happens naturally!

  16. Diffusion & Cells • Substances that can diffuse across cell membranes will do so until equilibrium is reached Diffusion continuesafterequilibrium but the rates are equalin ALL DirectionsAtoms & Molecules Never Stop Moving

  17. OSMOSIS

  18. Osmosis Requires A Membrane • Permeable Membrane • Substance Can Easily Cross • Impermeable Membrane • Substance Can NOT Cross • Selectively Permeable Membraneaka = Semipermeable Membrane • Some Substances Can Cross, Others Can Not • Cell Membranes are Semipermeable

  19. OSMOSIS Key Concept: Osmosis = The Diffusion Of WaterThrough A Selectively Permeable Membrane

  20. The Tonics • Hypotonic • Less concentrated solution • Isotonic • Equally concentrated solution • Hypertonic • More Highly concentrated solution

  21. The Tonics

  22. The Tonics

  23. How Osmosis Works • Overhead – Sugar & Water • Membrane Impermeable To Sugar • Water moves from a higher concentration of WATER to a lower concentration of WATER(NOT Sugar)

  24. Osmotic Pressure • Pressure exerted on the hypertonic side of a selectively permeable membrane • May cause cells to shrink or burst

  25. Osmotic Pressure Cell Membrane Contractile Vacuoles

  26. Facilitated Diffusion • Molecules that can easily diffuse across the cell membrane: • Alcohol • Water • Small Lipids

  27. Facilitated Diffusion • Other molecules can not pass through the cell membrane but still get into the cell. HOW?

  28. Facilitated Diffusion • Thru Protein Channels in the Cell Membrane that allow a substance to cross. • Allows Diffusion In Both Directions • Each Channel Substance Specific • DOES NOT REQUIRE ENERGY

  29. Facilitated Diffusion Protein Channel Is Substrate Specific Substrate Can Move Either Direction Depending On Concentration. Always from area of Higher Concentration to area of Lower Concentration!

  30. Active Transport • Moves Material Across A Cell Membrane • Against A Concentration Gradient (from area of Lower concentration into an area of Higher concentration)

  31. Active Transport Requires Energy

  32. Energy Molecule

  33. Active Transport

  34. Active Transport • Endocytosis • Used to bring in large molecules, food, and whole cells • Exocytosis • Membrane surrounded material from inside the cell fuses with the cell membrane, releasing the contents.

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