Adapting to extreme temperatures

Question 1

How are tolerance zones different?

Answer 1

Be narrow or broad
Differ both within and between populations
Change between seasons, life stages, condition, age etc.

Question 2

What is tolerance?

Answer 2

Capacity to endure conditions without adverse reaction

Question 3

What is the zone of tolerance?

Answer 3

Range in which at animal is most comfortable, is bounded by upper and lower zone of physiological stress.

Question 4

What factors affects tolerance to temperature?

Answer 4

Thermal history

Seasonal changes in temperature

Question 5

What are the primary functions of heat shock proteins>

Answer 5

To promote the proper folding or refolding of proteins
To prevent potentially damaging interactions with proteins
Aid in the disassembly of formations of protein aggregates

Question 6

How to heat shock proteins behave as molecular chaperones?

Answer 6

Stabilise other proteins
Minimise probability of inappropriate interactions
Involved in successful folding, assembly, regulation and degradation of other proteins

Question 7

Where do you find heat shock proteins?

Answer 7

Present in all major compartments of all cells of all animals, plants and prokaryotes

Question 8

Why are heat shock proteins important in stress?

Answer 8

Limit the consequences of damage from stress, and facilitate cellular recovery

Question 9

When are heat shock proteins produced?

Answer 9

In response to stress, increased levels occur

Question 10

What does stress do to proteins?

Answer 10

Causes them to unfold/denature, means they don’t function properly

Question 11

Why do Heat shock proteins not denature?

Answer 11

Because they have better and stronger H bonds and secondary structure, so are harder to denature

Question 12

What are the secondary functions of heat shock proteins?

Answer 12

Immune function:
Usually found intracellularly, so if found extracellularly
suggests that cell membranes have been damaged
Helps to present antigens from diseased cells to T cells, which destroy diseased cells
Serve as a warning signal to the body

Question 13

What happened in the experiment on drosophila where they engineered heat shock proteins to always be expressed?

Answer 13

Is very costly to produce, so showed a higher mortality and slower development

Question 14

What happens to cells at sub zero temperature?

Answer 14

Ice formation, external fluid freezes, solute concentration of external fluid increased so water leaves cells by osmosis. cells shrink and membrane structure is damaged

Question 15

What are the two strategies to deal with freezing temperatures?

Answer 15

Freeze avoidance and freeze tolerance.

Question 16

What is freeze avoidance and geographically where does it often occur?

Answer 16

Avoid freezing by keeping the bodily fluids liquid, occurs in northern hemisphere, where temperature is seasonal and for a long period of time

Question 17

What is freeze tolerance and geographically where does it occur?

Answer 17

Can tolerate the formation of internal ice, occurs in the Southern Hemisphere where seasonal cold temperatures are not as long or extreme

Question 18

What are the mechanisms of freeze avoidance?

Answer 18

Selection of a dry hibernation site in which no ice nucleation from an external source can occur
Physical barrier such as a wax-coated cuticle that provides protection against external ice across the cuticle
Depress the temperature at which bodily fluids will freeze

Question 19

What is supercooling?

Answer 19

Water requires a particle such as dust in order to crystallize (nucleate)
If no source of nucleation is introduced, water can cool to −42°C without freezing, so ice-nucleating agents in the gut or intracellular compartments are removed or inactivated
and water cools below its freezing point without changing phase into a solid, due to the lack of a nucleation source

Question 20

What is cryoprotectant synthesis?

Answer 20

An alteration of biochemistry, there is an increased solute concentration, which leads to a decreased freezing point
Most common with glycerol

Question 21

What are the mechanisms of freeze tolerance?

Answer 21

Limit supercooling, initiate freezing of body fluids at relatively high temperature
Produce ice structuring proteins - antifreeze
proteins, which bind to small ice crystals to inhibit growth/recrystallization of ice.

Question 22

Why is freeze tolerance beneficial?

Answer 22

Can control to what extent and where internal ice forms, means organisms can avoid a sudden total freeze, as can imitate freezing at higher temperatures and regulate it

Question 23

how do ice nucleating protein work with antifreeze proteins?

Answer 23

Ice nucleation proteins induce growth of single ice crystal nuclei, whilst antifreeze proteins inhibit any further growth

Question 24

Describe freeze tolerance in the Arctic woolly bear moth

Answer 24

Withstand -70oC during annual period of diapause
Accumulate cryoprotectants in late Arctic summer
Form hibernaculum to eliminate nucleators

Question 25

Describe freeze avoidance in Goldenrod gall moth larvae

Answer 25

Supercooling points dropped from -14oC to -38oC during autumn. Water content is decreased glycerol content increased

Question 26

How does the wood frog deal with freezing temperatures?

Answer 26

Supercools to -3oC. Survives weeks at -8oC in frozen state with 48% of total body water as ice – tolerates freezing of extracellular water. No anticipatory accumulation of cryoprotectants during autumn, this is triggered by initiation of ice formation in the body

Question 27

How does the red bark beetle deal with freezing temperatures?

Answer 27

Larvae can survive -150oC
High concentrations of glycerol
Ice-structuring proteins
Deliberately dehydrate tissues to concentrate ISPs so the body water forms a glassy substance rather than freezing