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Chapter 7 Cell Structure & Function

Chapter 7 Cell Structure & Function. Section 7-3 Movement Through The Membranes. Objectives. What are the main functions of the cell membrane and the cell wall? What happens during diffusion? What is osmosis?. The Cell Membrane. Key Concept:

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Chapter 7 Cell Structure & Function

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  1. Chapter 7Cell Structure & Function Section 7-3 Movement Through The Membranes

  2. Objectives • What are the main functions of the cell membrane and the cell wall? • What happens during diffusion? • What is osmosis?

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

  4. 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

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

  6. LIPID BILAYERS

  7. LIPID BILAYERS

  8. 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

  9. 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

  10. Cytoplasm Is A Solution Of Many Different Substances In Water

  11. 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

  12. Concentration Of Solution Mass of the solute in a given volume of solvent. Mass/Volumee.g. 12 g. of NaCl dissolved in 3L H2O = 12g./3 l. or 4.0 g/L

  13. 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 and area of lower concentration

  14. DIFFUSION • Molecules move away from an area of Higher Concentration to area’s of Lower Concentration • Equilibrium • Concentration of a solute is the same throughout the solution

  15. Diffusion

  16. DIFFUSION Key Concept: Diffusion Causes Many Substances To Move Across A Cell Membrane But: Does NOTRequire The Cell To Use Energy

  17. Diffusion across a membrane

  18. Diffusion & Cells • Substances that can diffuse across cell membranes will do so until equilibrium is reached • Diffusion continuesafterequilibrium but the rates in and out are equal

  19. OSMOSIS

  20. Osmosis • Permeable Membrane • Substance Can Easily Cross • Impermeable Membrane • Substance Can NOT Cross • Selectively Permeable Membrane • Some Substances Can Cross, Others Can Not

  21. OSMOSIS Key Concept: The Diffusion Of WaterThrough A Selectively Permeable Membrane

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

  23. The Tonics

  24. The Tonics

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

  26. Osmotic Pressure Cell Walls Contractile Vacuoles

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

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

  29. 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

  30. 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!

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

  32. Active Transport Requires Energy

  33. Energy Molecule

  34. Active Transport

  35. 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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