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Cell Membranes Osmosis and Diffusion

Cell Membranes Osmosis and Diffusion. Functions of Membranes. Protect cell Maintain homeostasis 3. Selectively permeable - allows some molecules in, others are kept out. Homeostasis. Balanced internal condition of cells Also called equilibrium

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Cell Membranes Osmosis and Diffusion

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  1. Cell MembranesOsmosis and Diffusion

  2. Functions of Membranes • Protect cell • Maintain homeostasis 3. Selectively permeable - allows some molecules in, others are kept out

  3. Homeostasis • Balancedinternal condition of cells • Also calledequilibrium • Maintained by cell membranecontrolling what enters & leaves the cell

  4. Phospholipid Bilayer Polar heads arehydrophilic“water loving” Nonpolar tails arehydrophobic“water fearing” Makes membrane“Selective”in what crosses

  5. Fluid Mosaic Model: “Proteins floating in a sea of lipids”

  6. Proteins Are Critical to Membrane Function

  7. Blood-Brain Barrier • Allows some substances into the brain, but screens out toxins and bacteria • Substances allowed to cross include: water, CO2, Glucose, O2, Amino Acids, Alcohol, and antihistamines. HIV and bacterial meningitis can cross the barrier.

  8. Solutions • Solutions are made of solute and a solvent • Solvent – The liquid part. It does the dissolving. • Solute – The thing being dissolved. Salt and sugar are solutes.

  9. Methods of Transport Across Membranes 1. Diffusion 2. Osmosis 3. Facilitated Diffusion 4. Active Transport

  10. Methods of Transport Across Membranes 1. Diffusion -passive transport - no energy used 2. Osmosis - Passive transport of water across membrane 3. Facilitated Diffusion – Needs a helper to get things across 4. Active Transport- requires energy to transport molecules against a concentration gradient – energy is in the form of ATP

  11. Diffusion • Movement of molecules from an area of high concentration to an area of low concentration. • Movement from one side of a membrane to another, without help.

  12. Diffusion

  13. Diffusion of Liquids

  14. Diffusion through a Membrane Solute moves DOWNconcentration gradient (HIGH to LOW) Cell membrane

  15. Facilitated Diffusion • Does NOT require energy • Uses transport proteins to move things from high to low concentration • Examples: Glucose or amino acids moving from blood into a cell.

  16. Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins.

  17. Facilitated Diffusion • This is a helper.

  18. Active Transport • Requires energy (ATP) • Moves materials from LOW to HIGH concentration AGAINST the concentration gradient.

  19. Osmosis • Diffusion of water across a membrane. • Moves from HIGH water amount (low solute) to LOW water amount (high solute). Diffusion across a membrane Semipermeable membrane

  20. You could think of it this way… • In osmosis, water FOLLOWS salt!! This is sometimes an easier way to remember this concept.

  21. The water is moving out of the cell. Why? Remember wherever salt is water follows! Where is the water moving? Salt SALT SALT

  22. Light blue = SaltDark blue = water

  23. There is a lot of salt outside of the cell. What will happen? Why?

  24. What will happen if there is a lot of salt inside of the cell?

  25. Normal In Salt Water What happened to the cytoplasm and cell membrane? Red Onion Cells

  26. Diffusion of H2O Across A Membrane High H2O potential (amount) andLow solute concentration Low H2O potential (amount) andHigh solute concentration

  27. Osmosis: Draw this

  28. Three Forms of Transport Across the Membrane

  29. Why does eating popcorn make you thirsty? Popcorn is very salty and may cause water to leave the cells of your mouth and through due to diffusion. This makes a person thirsty. Question

  30. When a sea urchin egg is removed from the ocean and placed in freshwater, the egg swells and bursts. Which of these causes water to enter the egg? • Coagulation • Sodium Pump • Active Transport • Osmosis D

  31. The picture shows a cell model and the solutions associated with it. In this situation the cell model will — • Gain mass • Shrink • Increase in solute content • Start to vibrate B

  32. Which of these best explains why a freshwater aquarium would be a dangerous habitat for saltwater fish? A The tissues of the saltwater fish would absorb too much acid. B The cells of the saltwater fish would lose too much water. C The organ systems of the saltwater fish would consume too much energy. D The cells of the saltwater fish would gain too much water. D

  33. On a hot summer day, a road-crew worker perspires and then feels thirsty as her body temperature increases. This response is an example of – • Releasing enzymes • Maintaining homeostasis • Decreasing respiration • Assimilating proteins B

  34. Think/Pair/Share • Work with a partner to create different situations that can be classified as diffusion. • Do the same for osmosis.

  35. Active Transport Video: http://www.iteachbio.com/Life%20Science/LifeFunctionsandTheCell/ActiveTransport.mov Diffusion Video: http://www.iteachbio.com/Life%20Science/LifeFunctionsandTheCell/Diffusion.mov Another Video: http://www.youtube.com/watch?v=ML-SWe5bRaE

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