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Membrane Transport Nestor T. Hilvano, M.D., M.P.H. (Images Copyright Discover Biology, 5 th ed., Singh-Cundy and Cain, Textbook, 2012.)

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Presentation on theme: "Membrane Transport Nestor T. Hilvano, M.D., M.P.H. (Images Copyright Discover Biology, 5 th ed., Singh-Cundy and Cain, Textbook, 2012.)"— Presentation transcript:

1 Membrane Transport Nestor T. Hilvano, M.D., M.P.H. (Images Copyright Discover Biology, 5 th ed., Singh-Cundy and Cain, Textbook, 2012.)

2 Learning Objectives 1.Describe plasma membrane and give its functions. 2.Differentiate the types of transport of molecules across the membrane. 3.Compare and contrast diffusion and osmosis. 4.Discuss briefly what happens when a red blood cells is placed in hypotonic solution? In hypertonic solution?

3 Plasma Membrane Functions: Regulates passage of ions and macromolecules in and out of the cell Allows some substances to cross more easily than others Allows information to be transferred across the membrane Possesses devices for cell attachment Receptors for hormones Ion pumps for regulating the internal environment

4 Components of Plasma Membrane The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it Selectively permeable Composed mainly of Bilayer of phospholipids (selective barriers), and some proteins, cholesterol, carbohydrates

5 Fig. 7-7 Fibers of extracellular matrix (ECM) Glyco- protein Microfilaments of cytoskeleton Cholesterol Peripheral proteins Integral protein CYTOPLASMIC SIDE OF MEMBRANE Glycolipid EXTRACELLULAR SIDE OF MEMBRANE Carbohydrate

6 Transport of Molecules Across the Plasma Membrane a)Passive transport- move from [high] to [low]; requires no ATP b)Active transport- move from [low] to [high]; needs ATP c)Facilitated transport- via carrier protein d)Exocytosis and endocytosis

7 Passive Transport Cell does not expend energy Diffusion – particles spread out from area of high concentration to an area of low concentration gradient. i.e. O 2 and CO 2 are small and nonpolar molecules that easily cross the membrane. Osmosis – is the net diffusion of water across a selectively permeable membrane

8 Figure 5.3A Molecules of dye Membrane Pores Net diffusion Equilibrium

9 Figure 5.4 Osmosis Solute molecule with cluster of water molecules Water molecule Selectively permeable membrane Solute molecule H2OH2O Lower concentration of solute Higher concentration of solute Equal concentrations of solute p. 76

10 Tonicity Tonicity is important in maintaining cell volume (ability to cause a cell to loss or gain water) Isotonic solution – solute concentration is the same both intracellular and extracellular An animal cell (RBC) placed in: Hypotonic – will gain water, swell and lyse Hypertonic – will lose water and crenate

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12 Facilitated Transport Uses specific transport proteins in the membrane Does not requires energy Substances move down its concentration gradient Channel proteins- ions channels (gated channel) that open or close in response to stimulus Carrier proteins- binds to protein and changes it’s shape

13 Fig EXTRACELLULAR FLUID Channel protein (a) A channel protein Solute CYTOPLASM Solute Carrier protein (b) A carrier protein

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15 Active Transport Requires expenditure of energy (ATP) Molecules move against the concentration gradient i.e. Na+ - K+ pump in nerve impulse transmission

16 Faciliatated diffusion and active transport:

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18 Endocytosis and Exocytosis Transport of large molecules Exocytosis – export bulky materials i.e. tearing, insulin release into the blood stream Endocytosis – cells take in macromolecules by forming vesicles/vacuoles from its plasma membrane. a) phagocytosis, b) pinocytosis

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21 Homework 1.Define – diffusion, osmosis, endocytosis, exocytosis, channel proteins, carrier proteins, isotonic solution, hypotonic solution, and hypertonic solution. 2.Describe the structure of plasma membrane and give its functions. What is it’s primary component? 3.Compare and contrast passive transport, facilitated transport, and active transport across a membrane as to concentration gradients, energy expenditure, use of carrier/transport proteins, and cite an example of substances. 4.Discuss the effect of hypotonic and hypertonic solution to red blood cells.


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