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Cell Membrane

Cell Membrane. Review of phospholipid bilayer. Monomers of fatty acids are used to build triacyglycerol (fats) and membrane lipids. 3:12. Hydrophobic effect. 2:20. A lipid bilayer prevents the diffusion of polar substances.

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Cell Membrane

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  1. Cell Membrane

  2. Review of phospholipid bilayer

  3. Monomers of fatty acids are used to build triacyglycerol (fats) and membrane lipids 3:12

  4. Hydrophobic effect 2:20

  5. A lipid bilayer prevents the diffusion of polar substances solutes spontaneously diffuse from a region of high concentration to a region of low concentration a lipid bilayer prevents the of polar substances of the inner compartment (also prevents the inward diffusion of polar substances) 3:13

  6. Cell Membrane – fluid mosaic model Composed of: • Lipids • double layer – • Proteins • surface • embedded proteins • Act as • Act as • Carbohydrates • Attached to surface on lipids or proteins • Many act as cards

  7. Cell Membrane • The cell membrane is permeable • Materials may cross the cell membrane in 3 methods: • through the membrane • Diffusion (passive transport) • Openings created via • Diffusion via channel (e.g. osmosis) • Diffusion via carrier (facilitated transport) • Carrier (active transport) • the cell membrane • Exocytosis or endocytosis (active transport)

  8. Cell Membrane is Selectively Permeable

  9. Transport of Molecules via Diffusion

  10. Factors effecting diffusion rate • gradient • of solute molecule • of medium (solvent) • Solubility of molecule (polarity/charge) • Temperature of • stream (continuous movement of cytoplasm moves molecules around the cell)

  11. Diffusion across a cell membrane • Diffusion: the of molecules from an area of concentration to an area of concentration until distributed • Diffusion is most rapid when there is a different in concentration (this is called the concentration gradient) • As the concentration decreases, the rate of diffusion • The rate of diffusion also depends on molecule and ; and the temperature and of the .

  12. Diffusion across a cell membrane

  13. Osmosis • Diffusion of H2O across a selectively permeable membrane • Every solution is made up of and the • Solute – the substance being • Solvent – the liquid that the is being dissolved within

  14. Osmosis • The of water across a cell membrane depends on the type of solution (the solute of the solution) on both sides of the barrier • The tonicity ( ) of a cell can be classified by the following : • Hypotonic – a solution with a solute concentration (and so more H2O ) compared to the other solution. • Hypertonic – The solution that has a solute concentration (and so less H2O ) compared the other solution • Isotonic – the solutions have H2O concentration

  15. Cells in Hypertonic Solutions • In hypertonic solutions, the of solute molecules the cell is higher than the concentration the cell • As a result, water out of the cell until equilibrium is • Cells in hypertonic solutions usually because the cells activities are by lack of • Scientific term when RBC shrinks is crenation

  16. Cells in Hypotonic Solutions • In a solution, the concentration of solute molecules the cell is lower than the of solutes inside the cell • Water will therefore flow into the until equilibrium is established • The flow of water into a cell causes it to • Scientific term when water enters the RBC is hemolysis

  17. Cells in Isotonic Solutions • In an isotonic solution, the concentration of solutes outside of the cell are • Water will therefore into and out of the cell at equal rates; there will be no movement of water

  18. Movement of Water *WATER WILL ALWAYS FLOW FROM HYPOTONIC TO A HYPERTONIC SOLUTION*

  19. : increase in vacuole's volume causes the cell membrane to push against the cell wall

  20. Transport of Molecules by Carriers

  21. Facilitated Transport • Follows the gradient, so therefore, it is a passive transport

  22. Facilitated Transport • Doesn’t require • Transports large molecules and charged ions since they cannot freely diffuse across the hydrophobic cell . • Carrier protein ( ) molecule in membrane is gated • CP molecule to be • CP to the molecule being • CP a conformational change and its gate opens and releases molecule to the other side • moves across the cell membrane in this manner

  23. Conformational Change in Proteins

  24. Active Transport • Requires energy since molecules move against the concentration gradient • Carrier protein molecule in membrane is gated • CP molecule to be transported • CP to the molecule being transported • ATP CP to open its gate to release the molecule to the side • Example: pump

  25. Sodium-Potassium Pump

  26. Endocytosis and Exocytosis

  27. Endocytosis • Is an process and energy • Other molecules which can’t cross the cell membrane through protein channels or carriers due to their size/type enter the cell via • During endocytosis, the membrane off the cell membrane and smaller vesicle is made, which carries the material being transported in • Two types on endocytosis:

  28. Phagocytosis • This type of is used by the immune system cells • Large or bacteria cells are engulfed by cell membrane • Fused with to break the bacteria down

  29. Pinocytosis • Other large taken in by the cell • Also known as “ ”

  30. Exocytosis • Getting rid of from the cytoplasm to the exterior of the cell • Membrane of the fuses with the cell membrane and discharges its

  31. What’s going on inside the cell?

  32. How the fluid mosaic model is established

  33. Fluid Mosaic Model • helps keep the membrane firm and prevents it from beings too fluidy • and are surface identification markers and play a role in cell-cell (what kind of cell is this? Good or bad?) • -sugar molecule attached to a phospholipid • – sugar molecule attached to a protein embedded in the membrane –

  34. Proteins in the cell membrane

  35. By the end of this section you should be able to: • Apply knowledge of organic molecules – phospholipids, proteins, glycoproteins, glycolipids, and cholesterol – to explain the structure and function of the fluid mosaic model • Identify the hydrophobic and hydrophilic regions of the phospholipid bilayer • Explain why the cell membrane is described and selectively permeable • Describe passive transport processes including diffusion, osmosis and facilitated transport • Explain factors that affect the rate of diffusion across a cell membrane (temperature, size of molecule, charge of molecule, concentration gradient, pressure gradient) • Predict the effects of hypertonic, isotonic and hypotonic environments on osmosis in animal cells • Describe the active transport process in terms of: concentration gradients, use of channel or carrier proteins, use of energy, types/sizes of molecules transported • Describe active transport processes such as endocytosis and exocytosis in terms of use of energy, type/size of molecules transported

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