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Transcript
CELL TRANSPORT TYPES OF TRANSPORT Passive Transport: does not require energy to move substances across the cell membrane Active Transport: requires energy to move substances across the cell membrane PASSIVE TRANSPORT VOCABULARY Equilibrium: when there is an equal number of molecules on both sides of the cell membrane Concentration: the amount of a particular substance in a given volume Concentration Gradient: When there is a higher concentration of a substance on one side than the other Diffusion: When a substance moves from an area of higher concentration to an area of lower concentration PASSIVE TRANSPORT When substances enter or leave the cell by diffusing across the cell membrane down their concentration gradient The direction the substances move depends on the concentration gradient TYPES OF PASSIVE TRANSPORT Simple Diffusion Facilitated Diffusion Osmosis SIMPLE DIFFUSION When small, nonpolar (uncharged) substances pass directly through the lipid bilayer from an area of higher concentration to an area of lower concentration Ex: If there is more oxygen outside the cell than inside the cell, it will diffuse across the lipid bilayer and into the cell. FACILITATED DIFFUSION Substances that cannot pass directly through the membrane are helped to diffuse through the membrane using transport proteins TRANSPORT PROTEINS Channel Proteins: Serve as a tunnel through the lipid bilayer that allow ions, sugars, and amino acids to pass through the membrane Each channel only allows specific substances to pass through Ex: The channel for sodium ions does not allow sugars to pass through TRANSPORT PROTEINS Carrier Proteins: Only transport substances that fit within their binding site through the cell membrane Carrier protein binds to a specific substance on one side of the cell membrane, changes shape and allows the substance out on the other side of the cell membrane OSMOSIS Facilitated diffusion of water from an area of higher concentration to an area of lower concentration Allows the cell to maintain water balance as their environment changes WATER CHANNELS Since water is a polar substance, it does not directly diffuse across the cell membrane So the cell has specific protein channels that only allow water to pass through PREDICTING WATER MOVEMENT The direction the water moves depends on the concentration of the cell’s environment HYPERTONIC Water moves out of the cell There is more solute outside the cell than inside the cell The cell loses water and shrinks HYPOTONIC Water moves in There is more solute inside the cell than outside the cell Cell gains water and expands ISOTONIC There is the same concentration of water inside the cell and outside the cell Equilibrium is reached Cell stays the same size ACTIVE TRANSPORT Transport of substances against their concentration gradients Requires energy usually in the form of ATP USE OF CARRIER PROTEINS AS PUMPS Carrier proteins require energy to pump substances across their concentration gradient SODIUM-POTASSIUM PUMP Sodium ions inside the cell bind to the carrier protein which changes shape and releases sodium ions outside the cell membrane As a result a phosphate group is released from the pump, returning the channel protein to its original shape, and releasing potassium ions inside the cell For every three sodium ions pumped out, two potassium ions are brought inside This prevents sodium from building up inside the cell, which would cause the cell to burst due to osmosis bringing in too much water VESICLES Large substances are too big to cross the membrane in channel proteins so they use vesicles Vesicle membranes are lipid bilayer, so they can bud off from the cell membrane or fuse with it to move large substances in or out of the cell ENDOCYTOSIS The movement of large substances into a cell using a vesicle The cell membrane forms a pouch around the substance that closes and then pinches off inside the cell Pinocytosis: also known as cellular drinking, engulfing liquid particles Phagocytosis: engulfing solid particles EXOCYTOSIS The movement of large substances out of a cell using a vesicle Vesicles inside the cell fuse with the cell membrane and are released outside the cell Used to transport proteins modified by the Golgi apparatus, excrete wastes, or remove bacteria