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Transcript
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 • CONCENTRATION: mass of solute dissolved in the solvent • SEMI-PERMEABLE (SELECTIVELY-PERMEABLE): a membrane that allows only some substances in or out Selectively Permeable Membrane Transportation of Molecules Passive Transport Active Transport • Movement of •Movement of molecules molecules across a across a semi-permeable semi-permeable membrane with the gradient membrane against a 3 types: Osmosis,Diffusion + concentration Facilitated Diffusion gradient with a protein •Movement of molecules across a semi-permeable membrane with a protein •NO ENERGY required • ENERGY required 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) 1 2 3 4 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] Osmosis Sucrose will not move but water will 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 Dialysis bag Glucose Iodine Starch Osmosis in Living Cells Cellulose in cell wall plasmolyzed flaccid Normal turgid RED BLOOD CELLS Osmosis in Plant Cells Plasmolysis • Observe Elodea leaves via a wet mount of the sample 10% NaCl Hypertonic Distilled water Hypotonic Recall the Cell Membrane Proteins in the Plasma (cell) Membrane Proteins are Specific to certain Solutes Active Transport 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