Cell Membranes and their Environment Materials must be able to move in and out of cells such as water oxygen food Wastes and carbon dioxide The cell conserve as much energy as possible during this process Diffusion the movement of molecules from an area of HIGH concentration to an area of LOW concentration NO energy is required which is great for the cell food dye This process is passive no energy is needed Unfortunately poisons such as carbon monoxide drugs and alcohol will diffuse into cells killing them The cell membrane is semipermeable some molecules can pass through while others can t due to concentration or size Osmosis the process of WATER moving from an area of HIGH to LOW concentration Equilibrium is achieved when the water molecules are moving in and out of the cell at the same rate The environment of a cell can be of 3 types One is normal the other two can kill the cell 1 Isotonic when the concentration of water molecules is the same in and out of the cell The concentration of other molecules called solutes is the same inside and outside the cell isotonic saline 2 Hypotonic This describes the environment of a cell that has a higher percentage of water molecules than inside the cell there is more water outside the cell than inside The water molecules move from high to low into the cell causing the cell to swell and break apart animal ceils In plant cells the vacuole will swell but the cell wall protects the cell from breaking drowning a When red blood cells gain water through osmosis the cell membrane stretches so much the cells appear clear they are called ghost cells 3 Hypertonic the situation in which the environment of the cell has LESS water than inside the cell water moves from HIGH to LOW concentration moving out of the cell faster than it moves in so the cell shrinks and dies An animal cell will shrink a plant cell s vacuole will shrink but the cell wall protects the cell a Animal cell are more fragile than plant cell because they don t have the strong cell wall b Active Transport When a cell uses energy to obtain molecules from LOW to HIGH concentration against the concentration gradient such as vitamins and minerals The cell uses ATP energy and helper proteins to drag the molecules into the cell from low to high concentration Vocabulary 1 plasmolysis when a cell loses water and shrinks 2 turgid in plant cells when the well vacuole gains water gives firmness and support to the cells 3 phagocytosis when a cell engulfs solid particles with its cell membrane and forms a food vacuole amoeba White blood cells 4 pinocytosis when a cell engulfs small fluid droplets
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