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Transport of Molecules in a Cell. Terms to Know. SOLUTE: refers to the substance that is to be dissolved (Salt, Sugar) SOLVENT : responsible for dissolving the solute (Water) SOLUTION : Solvent and solute after combining together ECF : Extracellular Fluid. Surrounds all living cells
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Terms to Know • SOLUTE: refers to the substance that is to be dissolved (Salt, Sugar) • SOLVENT: responsible for dissolving the solute (Water) • SOLUTION: Solvent and solute after combining together • ECF: Extracellular Fluid. Surrounds all living cells • CONCENTRATION: mass of solute dissolved in the solvent • SEMI-PERMEABLE (SELECTIVELY-PERMEABLE): a membrane that allows only some substances in or out
Active Transport Movement of molecules across a semi-permeable membrane against a concentration gradient with a protein ENERGY required Transportation of Molecules • Passive Transport • Movement of molecules across a semi-permeable membrane with the gradient • 3 types: Osmosis,Diffusion + • Facilitated Diffusion • Movement of molecules across a semi-permeable membrane with a protein • NO ENERGY required
1 4 2 3 Diffusion • Solute molecules moving from an area of high concentration to an area of low concentration • Random motion drives diffusion • Movement is based on kinetic energy (speed), charge, and mass of molecules • Equilibrium is reached when there is an even distribution of solute molecules (water)
Equilibrium Reached Low Concentration High Concentration
Osmosis • Diffusion of water through a semi-permeable membrane • Permeable to solvents (WATER), but not to large molecules • High [water] to low [water] [concentration] • Dissolved molecules (i.e. glucose, starch) are called solutes • REMEMBER: Water = solvent Glucose, Starch, Salt = solutes
Effect of Water on Cells • Hypertonic Environment • High [solute], low [water] • Isotonic Environment • [water] = [solute] • Hypotonic Environment • High [water], low [solute]
Dialysis bag Glucose Iodine Starch Dialysis Bag Experiment • Dialysis Bag • Semi-permeable membrane • Water, glucose, & starch • What passes through the dialysis bag? • Glucose (Benedict’s Test) • Starch (Iodine Solution) • Time Course Experiment • Every 10 minutes, measure the amount of glucose & starch present in the beaker
Cellulose in cell wall Osmosis in Living Cells plasmolyzed flaccid Normal turgid
Hypertonic Hypotonic Osmosis in Plant Cells Plasmolysis • Observe Elodea leaves via a wet mount of the sample • 10% NaCl • Distilled water
ENDOCYTOSIS The general term for bringing bulk chemicals into a cell is endocytosis (endo = inside); the general term for bringing bulk chemicals out of a cell is exocytosis (exo=outside). Moving material into the cell by endocytosis involves the pinching in of a portion of the cell membrane around the material to be transported into the cell. The pinched-in portion eventually breaks free from the cell membrane and forms a vesicle in the cytoplasm.
Homework • Complete your Cheek Cell & Elodea Cell mini-lab • Study for your Microscope quiz • Answer questions on p.25 Q.1-19 Next topic: Cell cycle & cell division