Temperature 5

Question 1

what are strategies used for surviving freezing temperatures (2)

Answer 1

• freeze-tolerance
• freeze-avoidance

Question 2

freeze-tolerance

Answer 2

• animals can allow their tissues to freeze and will tolerate it

Question 3

freeze-avoidance

Answer 3

• animals use behavioural and physiological mechanisms to prevent ice crystal formation

Question 4

supercooling (2)

Answer 4

• describes the phenomenon where water can remain liquid below 0C in teh absence of a nucleator
• can remain supercooled as low as 40C

Question 5

what does ice crystal formation require (2)

Answer 5

• a trigger
• cluster of water molecules or a macromolecule acts as a nucleator to trigger ice crystal formation

Question 6

what are the deleterious effects of ice crystal formation (2)

Answer 6

• points and edges can pierce membranes
• crystal growth removes surrounding water, increasing osmolarity

Question 7

how can the freezing point of a solution be depressed

Answer 7

• increasing the concentration of solute inside the solution

Question 8

what is the quantitative drop in freezing point with change in osmolarity

Answer 8

• freezing point drops 1.86C for every 1 Osmol/L

Question 9

what happens as a solution freezes (4)

Answer 9

• 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

Question 10

how do caterpillar larvae and larval beetles survive freezing temperatures (2)

Answer 10

• lower freezing point using glycerol
• 25-30% of body weight can by glycerol to tolerate extremely low temperature and remain active

Question 11

how does glycerol contribute to surviving freezing temperatures (2)

Answer 11

• depresses the freezing point of blood
• ice crystals freeze into beads rather than spicules in glycerol presence, inducing less damage

Question 12

how is glycerol formed

Answer 12

• synthesized by carbohydrate metabolism

Question 13

what are the terms used to describe solutes activity that prevents freezing (2)

Answer 13

• colligative cryoprotectant
• non-colligative cryoprotectant

Question 14

colligative cryoprotectant (2)

Answer 14

• 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

Question 15

non-colligative cryoprotectant (2)

Answer 15

• additional interactions by specific solutes that prevent freezing
• eg. how antifreezes inhibit ice crystal growth to prevent physical damage

Question 16

cryoprotectant examples (3)

Answer 16

• glycerol
• sorbitol
• trehalose

Question 17

what kind of cryoprotectants are glycerol, sorbitol, and trehalose

Answer 17

• sugars

Question 18

what indicates the use of glycerol, sorbitol and trehalose as cryoprotectants (2)

Answer 18

• glycogen falls over time in organisms that uses these cryoprotectants
• glycogen is required to synthesize them

Question 19

how do gall flies survive freezing temperatures (2)

Answer 19

• take advantage of colligative properties of water
• glycerol, sorbitol and trehalose increase in concentration to lower the freezing point

Question 20

what are examples of freeze-avoidance (3)

Answer 20

• supercooling
• depressing freezing points using colligative properties of water
• antifreeze molecules

Question 21

antifreeze molecules

Answer 21

• proteins or glycoproteins that depress the freezing point by noncolligative actions

Question 22

how do antifreeze molecules work (2)

Answer 22

• disrupt ice crystal formation
• bind small ice crystals and preventing growth

Question 23

what temperature do tissues freeze at

Answer 23

-0.5 to -0.7C

Question 24

freeze-avoidance: presence in freshwater fish (2)

Answer 24

• don’t experience freeze avoidance
• water freezes at 0C and tissues freezes before tissues do, so fish die before selection can occur

Question 25

freeze-avoidance: presence in marine fish

Answer 25

• seawater freezes at -1.86C, so marine organisms could freeze before water does, giving time for selection to occur

Question 26

freeze avoidance: mechanism in marine fish (3)

Answer 26

• polar fish synthesize glycoproteins and antifreeze proteins
• bind to and regulate ice crystal formation
• behaviourally avoid possible nucleation sites