Temperature 5 Flashcards
what are strategies used for surviving freezing temperatures (2)
- freeze-tolerance
- freeze-avoidance
freeze-tolerance
- animals can allow their tissues to freeze and will tolerate it
freeze-avoidance
- animals use behavioural and physiological mechanisms to prevent ice crystal formation
supercooling (2)
- describes the phenomenon where water can remain liquid below 0C in teh absence of a nucleator
- can remain supercooled as low as 40C
what does ice crystal formation require (2)
- a trigger
- cluster of water molecules or a macromolecule acts as a nucleator to trigger ice crystal formation
what are the deleterious effects of ice crystal formation (2)
- points and edges can pierce membranes
- crystal growth removes surrounding water, increasing osmolarity
how can the freezing point of a solution be depressed
- increasing the concentration of solute inside the solution
what is the quantitative drop in freezing point with change in osmolarity
- freezing point drops 1.86C for every 1 Osmol/L
what happens as a solution freezes (4)
- as ice crystals form, solutes are excluded and remain in solution
- excluded solutes depress freezing point (high osmolarity)
- remaining solution stays liquid even at low temperatures
- referred to as the colligative property of water
how do caterpillar larvae and larval beetles survive freezing temperatures (2)
- lower freezing point using glycerol
- 25-30% of body weight can by glycerol to tolerate extremely low temperature and remain active
how does glycerol contribute to surviving freezing temperatures (2)
- depresses the freezing point of blood
- ice crystals freeze into beads rather than spicules in glycerol presence, inducing less damage
how is glycerol formed
- synthesized by carbohydrate metabolism
what are the terms used to describe solutes activity that prevents freezing (2)
- colligative cryoprotectant
- non-colligative cryoprotectant
colligative cryoprotectant (2)
- depression of freezing point that is strictly dependent on number of molecules in a given volume
- eg. osmolarity related reductions in freezing point where the type of solutes do not matter
non-colligative cryoprotectant (2)
- additional interactions by specific solutes that prevent freezing
- eg. how antifreezes inhibit ice crystal growth to prevent physical damage
cryoprotectant examples (3)
- glycerol
- sorbitol
- trehalose
what kind of cryoprotectants are glycerol, sorbitol, and trehalose
- sugars
what indicates the use of glycerol, sorbitol and trehalose as cryoprotectants (2)
- glycogen falls over time in organisms that uses these cryoprotectants
- glycogen is required to synthesize them
how do gall flies survive freezing temperatures (2)
- take advantage of colligative properties of water
- glycerol, sorbitol and trehalose increase in concentration to lower the freezing point
what are examples of freeze-avoidance (3)
- supercooling
- depressing freezing points using colligative properties of water
- antifreeze molecules
antifreeze molecules
- proteins or glycoproteins that depress the freezing point by noncolligative actions
how do antifreeze molecules work (2)
- disrupt ice crystal formation
- bind small ice crystals and preventing growth
what temperature do tissues freeze at
-0.5 to -0.7C
freeze-avoidance: presence in freshwater fish (2)
- don’t experience freeze avoidance
- water freezes at 0C and tissues freezes before tissues do, so fish die before selection can occur
