Extreme environments Flashcards
What are extremophiles?
Organisms that thrive in extreme environments, mostly archaea and bacteria, except Tardigrades Tardigrades enter cryptobiosis metabolism drops to 0.01% normal, water content drops to 1% of normal replaces water with trehelose this sugar protects membranes from damage
Define adaptation
natural selection adjusts frequency of genes coding for traits affecting fitness
Define acclimatization
PHENOTYPIC PLASTICITY - phenotype will change to make the best out of the situation.
gives rise to short term changes in response to environmental disturbance
What are the three responses to environmental change?
AVOID - migrating/moving to microhabitat
CONFORM - change internal state so similar to imposed external state
REGULATE - animal tries to maintain internal environment (homeostasis) regardless of external conditions
usually requires metabolic energy
What does Q10 describe?
Effects of temperature on rate of function.
but of limited use
enzymes from lower body temperature species have higher substrte rates
col adapted enzymes have lower activation energy (but similar Km at normal working temperature
In reference to enzyme activity, what does k refer to?
Rate constant of the reaction
What is homeoviscous adaptation?
keeps membrane in fluid state
liquid crystals
General trend is increase unsaturated fatty acids at lower growth temperature + increase in saturated fatty acids at higher temperatures
lipid components 25-50% of membrane weight
what is the albedo effect?
ability of light colours to reflect more sun heats
What is freeze tolerance?
can cope with ice formation within the body
2 strategies:
confine ice crystals to extracellular fluids (and form them slowly)
protect cells from injury via CRYO-PROTECTANTS colligative and non colligative)
How do freeze-intolerant animals avoid?
No ice crystals forming due to supercooling and antifreezes.
Supercooling: dissolved solutes lower supercooling point of water.
Antifreezes: Glycerol, antifreeze glycopeptides. Antifreeze peptides
Describe the cell freezing process
Occurs due to nucleation of ice crystals
lower temperature, smaller number of water needed to make an “ice embryo”
freezing begins around in the gut
ice formation in tissues usually starts in extracellular fluid
non-frozen part of ECF becomes increasingly concentrated, compromises pure water
What are the problems of thawing?
too rapid swelling of cells
rapid re-introduction of oxygen can initiate burst of damage from oxygen free radicals
free radicals bind to protein, membranes, and DNA changing their structure
What are the 4 adaptations to temperatures below freezing?
cryptobiosis
vitrification - water becomes amorphous glass
freeze tolerance
freeze avoidance
What are the molecules that bring the freezing point of a solution lower than its melting point?
Supercooling agents
solutes added to body fluid to enhance supercooling properties
antifreeze compounds
