BIOL 1070 Chapter Notes - Chapter 11: Puijila, Ice Crystals, Cryoprotectant
28 Jul 2019
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Past arctic: climate used to be more temperate. E. g. puijila darwini: ancient form of modern seal: climate change happened before, but now faster rate. Osmosis: passive movement of water across membrane from high water conc. Low water conc. (low solute high solute) Hypertonic solutions: more solute outside, water leaves, cells shrink. Hypotonic solutions: less solute outside, water enters, cells swell. Isotonic solutions: no changes: tissues in below-freezing temp. Less water outside cell, more solute outside, higher osmotic pressure outside, cells shrink. Freezing or preventing it: tolerant freeze or prevent it. Cryoprotectants (sugars, glycerol) stabilize cells, prevent osmotic damage when extracellular fluids freeze, lower freezing point. Ice-nucleating agents (proteins, bacteria) form ice outside cells. Ina not used, gut contents emptied to prevent ice formation. Ice throughout body, extracellular fluid, body cavities: freeze solid over winter, under litter, glycerol collects before freezing, protects cell membrane, make much glucose to limit osmotic imbalance, so less dehydration of cells, adrenaline stimulates afp production.
