33. Osmoregulation2

33. Osmoregulation2 - Hydroregulation and Osmoregulation:...

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1 Hydroregulation and Osmoregulation: All about H 2 O (and Ions): All About Water (and Dissolved Solutes) Hydroregulation - the water content of an organism Osmoregulation - the solute content of an organism Water - universal solvent for almost all biological reactions Most organisms - well-defined, relatively constant solute conc in internal fluids (i.e., homeostasis) Hydroregulation and Osmoregulation Unity - 1) Common physical and molecular mechanisms for solute uptake (same as nutrient uptake!) 2) Osmosis - universal principle of passive water flow across membranes down its concentration gradient Diversity - 1) Wall-less cells – osmotic maintenance Walled cells - turgor maintenance 2) Environmental conditions - marine, freshwater, and terrestrial Active transport: 1) ATP hydrolysis generates H + or Na + electrochemical gradients http://www.pump.ruhr-uni-bochum.de F Fig. 6.26 Animals - Na + /K + pump Same basic process in bacteria, protists, plants, and fungi, except they use H + pumps to generate the H + electrochemical±gradient± F. Fig. 6.22
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2 2) Electrochemical gradients drive the uptake of ions for osmoregulation ATP-dependent H + pump Cation uniporter (into the cell) H + -anion cotransporter (into the cell) low H + negative high H + positive Animals - use Na + /K + pump, and Na + instead of H + Osmosis F. Fig 6.15 Osmosis - passive diffusion of water molecules across a semi- permeable membrane down their concentration gradient higher H 2 O lower H 2 O concentrations Big surprise - most pure lipid biomembranes allow only slow diffusion of water molecules Many bacterial and eukaryotic membranes have water channel proteins called aquaporins that mediate passive osmotic flow. Hypertonic Hypotonic Isotonic Physical process of osmosis Group discussion: Predict the direction(s) of water flows and their consequences for vesicle membranes •Hypertonic solution - higher solute concentration in solution relative to vesicle •Hypotonic solution - lower solute concentration in solution relative to vesicle •Isotonic solution - same solute concentration in solution and vesicle Basic terms for describing osmotic conditions F Fig 6.16 •Hypertonic solution - higher solute concentration in the solution relative to the vesicle
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This note was uploaded on 02/01/2012 for the course BSCI 207 taught by Professor Higgins during the Spring '08 term at Maryland.

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33. Osmoregulation2 - Hydroregulation and Osmoregulation:...

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