TRANSPORT!

Picky membrane The lipid bilayer is semipermeable Nonpolar molecules pass easily through the membrane Polar molecules (ions, water, etc) don’t pass through easily Transport proteins/ channel proteins Aquaporins Ion Channels

Move ‘em OUT! Substances are constantly moving through the cell membrane Passive Transport~ does not require any energy Active Transport~ needs ATP from the cell

Diffusion Diffusion~ tendency of any molecule to spread out into available space Concentration gradient~ difference in concentration across a space In passive transport, molecules always move down the concentration gradient

Diffusion will continue until the concentration of solute is evenly distributed throughout a space (equilibrium).

Osmosis Osmosis~ the diffusion of water across a selectively permeable membrane Hypertonic~ higher concentration of solutes Hypotonic~ lower concentration of solutes Isotonic~ equal concentrations of solutes

Osmoregulation = control of water balance Hypotonic- water moves into the cell Hypertonic- water moves out of the cell Isotonic- water movement is stable Cells with Walls: Turgid in hypotonic Flaccid in isotonic Plasmolyzed in hypertonic Plasmolysis~ plasma membrane pulls away from cell wall

Facilitated Diffusion Uses transport proteins Channel proteins Carrier proteins Passive Transport (no NRG needed) Passage of ions and large molecules

Active Transport Against concentration gradient Requires ATP Ion Pumps Set up a charge, or membrane potential, across membrane Ions flow with their electrochemical gradient

Sodium-Potassium Pump

Electrogenic pump Cotransport Proton pump Stores up voltage that can be used for cell processes Cotransport Molecules can “follow” ions back into the cell along their electrochemical gradient

Bulk Transport Exocytosis~ release of macromolecules by vesicles fusing with the plasma membrane Secretions How waste is released

Endocytosis~ import of macromolecules by forming new vesicles with the plasma membrane Phagocytosis (solids) Pinocytosis (liquids) receptor-mediated endocytosis (ligands)