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Chapter 4

Chapter 4. Membrane Structure and Function. Plasma Membrane. Fluid Mosaic Model. Cholesterol Reduces the amount of stuff allowed to enter a cell Phospholipids This is the lipid bilayer Glycolipids A carbohydrate that is attached to a phospholipid Proteins

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Chapter 4

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  1. Chapter 4 Membrane Structure and Function

  2. Plasma Membrane

  3. Fluid Mosaic Model • Cholesterol • Reduces the amount of stuff allowed to enter a cell • Phospholipids • This is the lipid bilayer • Glycolipids • A carbohydrate that is attached to a phospholipid • Proteins • Can help move things in and out of the cell • Glycoproteins • A carbohydrate that is attached to a protein

  4. The carbohydrates that come out of the plasma membrane allow cells to recognize each other • If a cell is not recognized the body tries to kill that foreign cell

  5. Permeability of Plasma Membrane • Plasma membrane is selectively permeable

  6. Selective Permeability • Selective permeability- Some things are let into the cell while some things remain outside of the cell

  7. Concentration Gradient • There is a greater concentration of small balls on one side than the other. This means that it will try to reach an equilibrium. • A gradient means that there is more on one side and gets less and less as you move to the other side

  8. Diffusion • Diffusion is the movement of molecules from a higher concentration to a lower concentration Time Semi-Permeable

  9. Diffusion • This occurs in our lungs. • High concentration of oxygen air enters lungs and O2 diffuses into our blood, which has a lower concentration of oxygen

  10. Osmosis • Osmosis is the diffusion of water • Water moves from a high concentration to a low concentration

  11. Water moves to the right because there is a difference in concentration • Osmotic pressure is the pressure that develops in a system because of osmosis

  12. Factors that will affect the rate of Diffusion • Temperature  higher temp. the faster the rate of diffusion • Size of molecule the smaller the molecule then the faster the rate of diffusion • Charge of molecule charged molecules have difficulty moving through the cell • Concentration Gradient  the larger the difference in concentration the faster the diffusion • Pressure Gradient  If there is pressure on one side then the faster the diffusion

  13. What happens to a cell in a solution • Tonicity – concentration of the solution compared to the concentration inside the cell • Isotonic • The concentration of the solution is equal to that of inside the cell • Hypotonic • Solution has a lower concentration of solute (higher concentration of water) than inside the cell • Hypertonic • Solution has higher concentration of solute than inside the cell

  14. What happens to a cell in solution • Isotonic solution • The cell remains the same. No changes • Hypotonic solution • The cell swells and may undergo lysis • Hypertonic solution • The cell loses water and shrivels. Or undergoes crenation

  15. Which is which? Hypertonic Isotonic Hypotonic

  16. Facilitated Transport • This is for molecules that are too big to diffuse through the plasma membrane • Proteins help them move • It stills move with the concentration gradient • It uses NO ENERGY

  17. Diffusion Facilitated Transport

  18. None of these use Energy So therefore they are called “Passive Transport” • Facilitated Transport • Diffusion • Osmosis

  19. Active Transport • This uses energy • ATP ADP • It moves molecules and ions against a concentration gradient • An example of active transport is the sodium potassium pump • Sodium is moved to the outside and potassium is moved to the inside of the cell

  20. Endocytosis and Exocytosis • These processes are used for materials that are too big to pass through the plasma membrane by a protein transport • Endocytosis • The cell engulfs material to bring it into the cell • Two types • Phagocytosis • Pinocytosis • Exocytosis • Moves material to the outside of the cell • This allows cell to secrete molecules

  21. Endocytosis • Phagocytosis • A type of endocytosis that engulfs large items. Like cells or bacteria • The vesicle that forms afterwards combines with lysosomes so digestion can occur

  22. Endocytosis • Pinocytosis • This is when very small particles are engulfed by the membrane • Receptor mediated endocytosis is a type of pinocytosis that uses receptor proteins to help initiate pinocytosis

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