LIFESCI 1 Lecture Notes - Lecture 22: Gastrointestinal Tract, Cloaca, Solution
Document Summary
Permeable = water and solutes can diffuse freely. Semipermeable = combo of lipid bilayer and transmembrane proteins. Impermeable = blocks off diffusion entirely: plasma membranes and sheets of cells that are semipermeable allow water and small solutes to pass through but not larger solutes (like proteins) Water can move directly through lipid bilayers (diffusion) or through channels (aquaporins: osmotic pressure = different in concentrations of solutes on 2 sides the membrane drives movement of water. Higher solute concentration = higher osmotic pressure (greater tendency for water to move into the solution) High osmotic pressure inside cell can be damage it and burst. Can tolerate up to 50% of cell dehydration. Excessive dehydration = impairs metabolic function: hydrolysis and other reactions to build proteins and nucleic acids depend on water. Achieved by movement of solutes (especially electrolytes) Balance input and output of water and electrolytes by drinking water less concentrated in solutes than body fluids: hypotonic .
