Living in Extreme Temperatures Flashcards
What is an example of behavioural control of thermoregulation?
Repositioning body in the environment to control body temperature
What are zones of temperature tolerance bounded by?
Zones of physiological stress
What is tolerance of temperature affected by?
Species
Populations
Life-stages
Individuals
What are heat shock proteins?
Molecular chaperones
Limit consequence of damage from heat stress
What are the primary functions of heat shock proteins?
Promote proper folding or refolding of a protein
Prevent potentially damaging interactions with proteins
Aid in disassembly of formations of protein aggregates
What are the three types of heat shock proteins?
Constitutively expressed (expressed under normal conditions)
Increased during and after stressed
Exclusively induced by stress
Why don’t heat shock proteins denature like other proteins?
Better hydrogen bonds
Better/more stable secondary structure
Still only have a limited range of conditions
What is the secondary function of heat shock proteins?
Immune function:
Helps present antigens from diseased cells to T cells
Why are heat shock proteins not always expressed?
Greater mortality
Slower development
What happens in sub-zero temperatures?
Ice formation
External fluid freezes so solute concentration of external fluid increases so water leaves cells - cells shrink
Cell membrane structure degrades
Ectotherms risk extracellular fluid freezing
Ice crystals can form intra and extracellularly - crystals are pointy and can cause cell damage
What are the strategies for freezing temperatures?
Freeze avoidance:
Keep body fluids liquid
In temperate northern hemisphere
Many endotherms migrate
Freeze tolerance:
Can tolerate internal ice formation
Not possible to stop ice crystal formation in certain temperatures
In artic and antarctic regions
How is freeze avoidance carried out?
1) Selection of dry hibernation site - stops ice formation from external water source
2) Physical barrier such as wax-coated cuticles - provides protection against external ice
3) Depress temperature at which bodily fluids freeze aka supercooling
What is supercooling?
Ice-nucleating agents in gut and intracellular compartments are removed or inactivated
Means there is no source of nucleation site so water can cool to -42C without freezing
Product cryoprotectants
What do cryoprotectants do?
Increase solute concentration so freezing point decreases (keeps water inside cells and reduced cellular dehydration)
What is the most common cryoprotectant?
Glycerol
