NATS 4210 Lecture Notes - Lecture 5: Cryoprotectant, Ice Crystals, Cryobiology
5 Nov 2016
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Animal adaptations below 0 degrees: freeze tolerance - allow tissues to freeze & encourage extracellular ice formation. Some insects survive ice forming in their bodies: insects can accumulate large concentrations of colligative antifreezes such as glycerol, sorbitol and mannitol (15-25% of their overwintering body weight) Ice nucleation encouraged by proteins, food/bacteria in gut, inoculative freezing. Cryoprotective measures prevent the intracellular from freezing, there"s ice-active proteins that inhibit recrystalisation, small molecule cryoprotectants (glycerol: free avoidance - use behavioral or physiological mechanisms to prevent ice crystal formation & growth. Some insects survive by avoiding freeze (prevents ice forming in their body: insect afps are more effective than those in polar fishes. Ice nucleation by: emptying the gut, avoiding surface moisture, masking/removing ice-nucleating agents. Antifreeze measures include small molecule antifreezes (glycerol), antifreeze proteins to inhibit ice crystal growth, and partial desiccation. Supercooling is a riskier strategy compared with antifreezes animals must avoid innoculative freezing.
