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Dehydration

Dehydration

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Dehydration

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  1. Dehydration Christina Ramirez Erek Dyskant

  2. Why we need water? • More than 2/3 of our weight • Joints • Temp regulation • Regulates metabolic reactions • Protein stability/folding and kinetics

  3. How we lose water? • Urine • Sweat • Vomiting • Diarrhea • Respiration *How much urine do we output a day?* *How much water do we take in? (in any form) Water and electrolytes are lost

  4. Our responses to dehydration

  5. Plant Responses to Dehydration

  6. Structural Plant Adaptations • Cacti • Wide surface root systems • Many roots, towards surface of soil • Absorbs rain water very quickly, so it can capture water from storms • Accordion structure • Allows cacti to expand during wet season, and contract droughts, preventing collapse and reducing exposed surface area. • Thorns channel water to base of plant

  7. Mesquite • Less water storage than cactus • Single very deep root. • Seasonal variation • During hot/dry season • Loses leaves to conserve water • Chlorophyll concentration decreases, slowing metabolism.

  8. Cell Membrane • Two bilayer phases • Liquid crystalline phase • Gel Phase

  9. Problems in membrane • Low water potential • Polar head group no longer hydrated • Van der Waals • Tm

  10. Rehydration • Tm • leaky membrane • Disaccharides help! • Tm ? Sucrose and trehalose

  11. Sucrose and Trehalose • [solute] increases osmotic pressure Crowe believes • Water replacement theory • Vitrification

  12. Vitrification • Ice • Stabilize • High viscosity • Tm • Reverses with the addition of water • Tg solidviscous

  13. What am I?

  14. Active Dehydrated at high humidity

  15. Low humidity Anesthetized

  16. Frog Aestivation • Australian frogs borrow into mud as temporary ponds dry up, and can stay dormant for up to a year. • Doesn’t remove waste • Urea content in muscles is 8 times that of hydrated frogs • They may have hormones which are not interrupted by urea, allowing them to maintain a higher urea concentration • The urea buildup may serve as a mechanism to slow their metabolism • Muscles don’t atrophy, as they do if the frog is anesthetized for the same amount of time

  17. Desiccation • Complete loss of water, to equilibrium with the air. • Seeds, and very select group of plants/animals are able to do this. • In seeds, the proteins necessary for desiccation are already present • In grown plants, the proteins are expressed when they’re needed

  18. Resurrection Plant • Small number of plants can desiccate themselves virtually completely • In callus tissue, it only becomes desiccation-resistant when ABA is administered first. • In full plants, ABA level goes up as the plant is deprived of water. Several hundred genes are expressed, mostly late embryogenesis abundant proteins. • When the plant is deprived of water, it produces ABA. • However, if a plant is mutated so that CDT-1 gene is constitutive, ABA is not required for desiccation tolerance in callus tissue. • Several hundred genes are expressed. A large number of them are hydrophilic proteins. • Hydrated leaves have high

  19. Carbohydrate Metabolism • Octulose is an intermediary sugar in photosynthesis. Resurrection plants horde it. • As a plant dehydrates, it’s converted to sucrose, and then during rehydration, converted back to octulose. • In C3 plants, octulose concentration goes up during day, and at night is converted to sucrose. • It’s like that the same enzymes that are responsible for octulose conversion in all C3 plants are also used during dehydration/rehydration. • Crowe finds that sucrose prevents protein denaturation.