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Movement Across a Membrane

Solutions and Transport. Solution homogeneous mixture of two or more componentsSolvent dissolving mediumSolutes components in smaller quantities within a solutionIntracellular fluid nucleoplasm and cytosolInterstitial fluid fluid on the exterior of the cell. Selective Permeability. The

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Movement Across a Membrane

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    1. Movement Across a Membrane

    2. Solutions and Transport Solution – homogeneous mixture of two or more components Solvent – dissolving medium Solutes – components in smaller quantities within a solution Intracellular fluid – nucleoplasm and cytosol Interstitial fluid – fluid on the exterior of the cell

    3. Selective Permeability The plasma membrane allows some materials to pass while excluding others This permeability includes movement into and out of the cell

    4. Cellular Physiology: Membrane Transport Membrane Transport – movement of substance into and out of the cell Transport is by two basic methods Passive transport No energy is required Active transport The cell must provide metabolic energy

    5. Passive Transport Processes Diffusion Particles tend to distribute themselves evenly within a solution Movement is from high concentration to low concentration, or down a concentration gradient

    6. Passive Transport Processes Types of diffusion Simple diffusion Unassisted process Solutes are lipid-soluble materials or small enough to pass through membrane pores Facilitated diffusion Substances require a protein carrier for passive transport Osmosis – simple diffusion of water Highly polar water easily crosses the plasma membrane

    7. Diffusion through the Plasma Membrane

    8. Active Transport Processes Transport substances that are unable to pass by diffusion They may be too large They may not be able to dissolve in the fat core of the membrane They may have to move against a concentration gradient Two common forms of active transport Solute pumping Bulk transport

    9. Active Transport Processes Solute pumping Amino acids, some sugars and ions are transported by solute pumps ATP energizes protein carriers, and in most cases, moves substances against concentration gradients

    10. Active Transport Processes

    11. Active Transport Processes Bulk transport Exocytosis Moves materials out of the cell Material is carried in a membranous vesicle Vesicle migrates to plasma membrane Vesicle combines with plasma membrane Material is emptied to the outside

    12. Exocytosis

    13. Active Transport Processes Bulk transport Endocytosis Extracellular substances are engulfed by being enclosed in a membranous vescicle Types of endocytosis Phagocytosis – cell eating Pinocytosis – cell drinking

    14. Endocytosis

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