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Transcript
Cell Transport Facilitated Diffusion Cells in their Environment Active Transport Passive Transport 1. Diffusion- movement of molecules from an area of high concentration to an area of low 2. Osmosis- process by which water molecules diffuse across a cell membrane from an area of high concentration to an area of low 3. Facilitated Diffusion- used for molecules that cannot readily diffuse through cell membranes, even when there is a concentration gradient… Facilitated Diffusion Facilitated Diffusion- carrier proteins in the cell membrane assist molecules that cannot readily diffuse across the cell membrane Molecules cannot diffuse because: May be not soluble in lipids May be too large to pass through Carrier proteins move molecules from a higher to lower concentration, so no energy is required… so it is PASSIVE TRANSPORT! http://www.northland.cc.mn.us/biology/Biolo gy1111/animations/active1.swf Example of Facilitated Diffusion Example= Glucose Cells depend on glucose for energy glucose molecules are too large to diffuse by simple diffusion When glucose levels in cell are lower than outside the cell, carrier proteins transport glucose in Cells in Hypotonic/ Hypertonic Environments Cells exposed to an isotonic environment usually have no trouble keeping the movement of water across the membrane in balance. It is more difficult for cells in a hypotonic/hypertonic environment Contractile Vacuoles Turgor Pressure Plasmolysis Cytolysis Contractile Vacuoles Unicellular freshwater organisms that live in a hypotonic environment use contractile vacuoles to rid excess water Contractile Vacuoles- organelles that collect excess water and then contract to pump the water out of the cell Pumping action requires cell to expend energy, it is not a form of passive transport Cytolysis Red Blood Cells- Lose their normal shape when exposed to an environment that is not isotonic Hypertonic environment = water leaves/ cells shrink and shrivel Hypotonic environment = water diffuses into cell/ cells swell and burst Cytolysis Cytolysis – bursting of cells Turgor Pressure Most plant cells live in hypotonic environment- water moves into plant cells by osmosis Cells fill as they swell with water until cell membrane is pressed against cell wall Cell wall resists pressure exerted by water Turgor Pressure- the pressure that water molecules exert against cell wall Plasmolysis Plasmolysis- cells are in a hypertonic environment and water leaves through osmosis. Cells shrink away from the cell walls (turgor pressure is lost) This is the reason plants wilt if they don’t receive enough water Active Transport Active Transport- movement of materials from an area of lower concentration to an area of higher concentration. Requires a cell to expend energy. 1. Endocytosis 1. 2. 2. 3. Pinocytosis Phagocytosis Exocytosis Sodium-Potassium Pumps Endocytosis Endocytosis- process by which cells ingest external fluid, macromolecules, and large particles 1. Pinocytosis- transport of solutes/ fluids 1. 2. External materials are enclosed by a portion of the cells membrane- folds into itself/ forms a pouch Pouch pinches off and becomes a vesicle http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/pinocyt.html Phagocytosis- movement of large particles 1. http://student.ccbcmd.edu/~gkaiser/biotutorials/eustruct/phagocyt.html Exocytosis Exocytosis- process by which a substance is released from the cell through a vesicle (reverse of endocytosis) Vesicles release their contents to the cell’s external environment Ex: large molecules such as proteins, waste products, toxins http://www.coolschool.ca/lor/BI12/unit4/U04L05/exocytosis.html Sodium-Potassium Pumps Sodium-Potassium pump – moves substance (ions) from lower to higher concentration/ require energy Energy needed for active transport is supplied directly or indirectly by ATP http://highered.mcgraw-hill.com/olc/dl/120068/bio03.swf