temperature Flashcards
Van’t hoff equation
Q10 = (k2/k1)^(10/[t2-t1])
k2 and k1 = rates of the rxn at temperatures at t2 and t1
for rxn at exactly 10C: Q10=k2/k1
for a 10C change in T, most chemical rxn rate….
doubles or triples
2 thermal strategies
tolerance (body temp can vary w/ ambient temp)
regulation (body temp does not vary with ambient temp)
total thermal energy equation
dHtotal = dHmetabolism + dHconduction + dHconvection + dHradiation + dHevaporation
d=delta
H=heat
heat transfer mechanisms
conduction: direct contact
radiation: electromagnetic radiation
convection: moving medium (air/water)
evaporation: latent heat of evaporation (heat loss only)
what is the role of anatomy and behaviour in heat transfer
anatomy: surface area + surface insulation affects rates of heat exchange; respiratory organs are better at transferring heat than O2
behaviour: can alter rates of heat exchange (move to a different environment, rest, etc)
what is thermal conductivity?
what happens to heat if there is high conductivity?
formula
ability of heat energy to move within a material
high conductivity (move heat easily) = poor insulation
Fourier’s law: Q=lambda deltaT/L
Q=heat flux
lambda= thermal conductivity
deltaT=temp gradient
L=distance over which gradient extends
what is heat capacitance?
what does it influence?
ability to store heat energy (water can store more heat than air)
influence: life in water vs. air, insulation materials, behaviour
what is something that influences ALL aspects of heat exchange?
surface area to volume ratio
high ratio= high rates of heat exchange
ratio decrease w/ body size
large animals exchange heat more slowly than small snimals
what is Bergmann’s rule
mammals and birds living in cold environments tend to be larger
larger animal-> smaller area to volume ratio-> exchange/lose heat more slowly
what is Allen’s rule
mammals and birds in colder climates have smaller extremities (smaller appendages)
what else can be done to help exchange heat (2)
body posture-> alter exposed surface area
huddling reduces effective surface area
thermal strategies (4)
poikilotherm: variable body temp
homeotherm: stable body temp
ectotherm: environment determines body temp
endotherm: generates internal heat
temporal and regional endothermy
temporal heterotherms: changes over time (hibernating animals)
regional heterotherms: body temp varies in regions of body
what is regional endothermy?
localized warming of red skeletal muscle used for sustained locomotion
heat produced by red muscle is retained there
countercurrent arrangement of arterioles and venules transmits heat from venous to arterial blood retaining heat
significance of regional endothermy
allow faster contraction frequencies
how does heater tissue in billfish eye provide regional endothermy
action potential-> activates Ca2+ release into cytosol from sarcoplasmic reticulum-> sarcoplasmic reticulum takes Ca2+ back up but needs ATP-> producing ATP generates heat
thermal zones of homeotherms
thermoneutral zone: range of temp optimal for physiological processes, metabolic rate minimal
upper crit temp: metabolic rate increases as animal induces physiological response to prevent overheating
lower crit temp: metabolic rate increases to increase heat production
describe the thermal tolerance of poikilotherms
no thermoneutral zone, uct or lct
preferred temp= ambient temp for optimal physiological function
range of tolerance is between incipient upper lethal temperature and incipient lower lethal temperature
incipient lethal temp= ambient temp where 50% of animals die
what is thermal tolerance
range of temperature where animals can survive but not necessarily thrive
how does one quantify thermal tolerance
eurytherm: can tolerate a wide range
stenotherm: can tolerate only a narrow range (usually polar/tropical bc their environment doesn’t change much)
what is aerobic scope?
energy available for activity above and beyond resting
aerobic scope= maximal - resting metabolic rate
why does aerobic scope decline at higher temperatures in an ectotherm?
proteins start denaturing / stop functioning
how does temp influence membrane fluidity?
Van der Wall’s forces hold membrane lipids together
low temp-> membrane lipids solidify
high temp-> membrane fluidity up
membrane fluidity is maintained relatively constant in animals at their respective body temp
what is homeoviscous adaptation?
significance?
maintain membrane fluidity at diff temp by changing composition of membrane lipids
membrane fluidity can affect protein movement
how is homeoviscous adaptation accomplished
fatty acid chain length: shorter=high fluidity
saturation: more double bond= high fluidity
phospholipid classes: PE= high fluidity
cholesterol content: prevents solidifying when membrane is cooled
what do heat shock proteins do
molecular chaperones that catalyze protein folding and help refold denatured proteins
endothermy requires ability to regulate
thermogenesis + heat exchange w/ environment
heat is a by-product of metabolic processes such as…
why would cells want leaky membrane to generate heat?
energy metabolism, digestion, muscle activity
need more ATP to maintain Na+/K+ gradient-> more ATP more heat
how do insects produce heat prior to flight
carbohydrate metabolism in flight muscles
antagonistic flight muscles contract simultaneously (like shivering)
describe shivering thermogenesis
unique to birds + mammals
uncoordinated myofiber contraction resulting in no gross muscle contraction
works for short periods of time
how do brown adipose tissue play a role in thermoregulation
used for nonshivering thermogenesis
brown adipose tissue is packed w/ leaky mitochondria-> futile cycling of mitochondria-> generate heat
how do countercurrent heat exchangers work to prevent heat loss birds
thermal energy is transferred from warm arterial blood to cooler venous blood-> heat retained (heat does not reach end of foot)
how do countercurrent heat exchangers work to prevent heat loss in mammals
nasal countercurrent heat exchanger operates to recycle and conserve water and prevent heat loss
heat of outgoing air is reabsorbed by surface of nasal pathway
what makes sweating an effective way of cooling down
reduce temperature by evaporative cooling
NaCl in sweat raises heat of vaporization-> greater heat loss than pure water
strategies for surviving freezing temp
freeze tolerance (can allow tissues to freeze)
freeze avoidance (behavioural + physiological mechanism to prevent ice crystal formation)
why is ice crystal formation an issue?
how can it be avoided?
points and edges can pierce membranes
crystal growth removes surrounding water, osmolarity up
avoid by preventing nucleator from forming
how can we depress the freezing point
by increasing conc. of solutes
sugars + salts don’t form into ice crystals, all concentrate in remaining liquid-> high osmolarity low freezing point
can also use glycerol
diff between colligative and non-colligative cryoprotectant
colligative: depression of freezing point by changes in osmolarity
non-colligative: additional interactions that prevent freezing eg inhibit crystal growth
2 mechanisms of freeze-tolerance
produce nucleators outside of cell (extracellular fluid freezes but intracellular fluid remains liquid)
produce intracellular solutes to counter movement of water
in frogs, freezing is restricted to…
what does the animal do to prepare
blood (ECF) only, not inside cells
animals activate genes required to make osmolytes to lower freezing point (sugars like sorbitol, glucose, glycogen glycerol) + nucleating agents
what are nucleating agents
compounds that ice can rapidly form around
why is the cell dehydrated when part of the animal is frozen?
ice crystals form in blood-> osmolytes concentrated freezing point down-> increased blood osmolarity draws water from cell by osmosis
dehydration tolerance associated w. freeze tolerance
what is super cooling?
in the absence of a nucleator, water can remain liquid below the freezing point of the fluid
how do antifreeze macromolecules work?
disrupt ice crystal formation by binding to small ice crystal and preventing growth
(noncolligative)
why do freshwater breathing fishes not really have to worry about freeze avoidance when there is water around?
water will freeze before tissues do
how can polar fishes withstand water temp below freezing temp of tissues
anti-freeze proteins that inhibit crystal growth (vs. antifreeze mechanism in frogs promote crystal growth extracellularly)
metabolically costly to make but need very little
