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biol 364 > temperature > Flashcards

temperature Flashcards

1
Q

Van’t hoff equation

A

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

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2
Q

for a 10C change in T, most chemical rxn rate….

A

doubles or triples

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3
Q

2 thermal strategies

A

tolerance (body temp can vary w/ ambient temp)

regulation (body temp does not vary with ambient temp)

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4
Q

total thermal energy equation

A

dHtotal = dHmetabolism + dHconduction + dHconvection + dHradiation + dHevaporation

d=delta
H=heat

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5
Q

heat transfer mechanisms

A

conduction: direct contact
radiation: electromagnetic radiation
convection: moving medium (air/water)
evaporation: latent heat of evaporation (heat loss only)

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6
Q

what is the role of anatomy and behaviour in heat transfer

A

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)

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7
Q

what is thermal conductivity?
what happens to heat if there is high conductivity?

formula

A

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

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8
Q

what is heat capacitance?
what does it influence?

A

ability to store heat energy (water can store more heat than air)

influence: life in water vs. air, insulation materials, behaviour

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9
Q

what is something that influences ALL aspects of heat exchange?

A

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

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10
Q

what is Bergmann’s rule

A

mammals and birds living in cold environments tend to be larger

larger animal-> smaller area to volume ratio-> exchange/lose heat more slowly

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11
Q

what is Allen’s rule

A

mammals and birds in colder climates have smaller extremities (smaller appendages)

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12
Q

what else can be done to help exchange heat (2)

A

body posture-> alter exposed surface area
huddling reduces effective surface area

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13
Q

thermal strategies (4)

A

poikilotherm: variable body temp
homeotherm: stable body temp

ectotherm: environment determines body temp
endotherm: generates internal heat

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14
Q

temporal and regional endothermy

A

temporal heterotherms: changes over time (hibernating animals)

regional heterotherms: body temp varies in regions of body

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15
Q

what is regional endothermy?

A

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

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16
Q

significance of regional endothermy

A

allow faster contraction frequencies

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17
Q

how does heater tissue in billfish eye provide regional endothermy

A

action potential-> activates Ca2+ release into cytosol from sarcoplasmic reticulum-> sarcoplasmic reticulum takes Ca2+ back up but needs ATP-> producing ATP generates heat

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18
Q

thermal zones of homeotherms

A

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

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19
Q

describe the thermal tolerance of poikilotherms

A

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

20
Q

what is thermal tolerance

A

range of temperature where animals can survive but not necessarily thrive

21
Q

how does one quantify thermal tolerance

A

eurytherm: can tolerate a wide range

stenotherm: can tolerate only a narrow range (usually polar/tropical bc their environment doesn’t change much)

22
Q

what is aerobic scope?

A

energy available for activity above and beyond resting

aerobic scope= maximal - resting metabolic rate

23
Q

why does aerobic scope decline at higher temperatures in an ectotherm?

A

proteins start denaturing / stop functioning

24
Q

how does temp influence membrane fluidity?

A

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

25
Q

what is homeoviscous adaptation?
significance?

A

maintain membrane fluidity at diff temp by changing composition of membrane lipids

membrane fluidity can affect protein movement

26
Q

how is homeoviscous adaptation accomplished

A

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

27
Q

what do heat shock proteins do

A

molecular chaperones that catalyze protein folding and help refold denatured proteins

28
Q

endothermy requires ability to regulate

A

thermogenesis + heat exchange w/ environment

29
Q

heat is a by-product of metabolic processes such as…

why would cells want leaky membrane to generate heat?

A

energy metabolism, digestion, muscle activity

need more ATP to maintain Na+/K+ gradient-> more ATP more heat

30
Q

how do insects produce heat prior to flight

A

carbohydrate metabolism in flight muscles

antagonistic flight muscles contract simultaneously (like shivering)

30
Q

describe shivering thermogenesis

A

unique to birds + mammals

uncoordinated myofiber contraction resulting in no gross muscle contraction

works for short periods of time

31
Q

how do brown adipose tissue play a role in thermoregulation

A

used for nonshivering thermogenesis

brown adipose tissue is packed w/ leaky mitochondria-> futile cycling of mitochondria-> generate heat

32
Q

how do countercurrent heat exchangers work to prevent heat loss birds

A

thermal energy is transferred from warm arterial blood to cooler venous blood-> heat retained (heat does not reach end of foot)

33
Q

how do countercurrent heat exchangers work to prevent heat loss in mammals

A

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

34
Q

what makes sweating an effective way of cooling down

A

reduce temperature by evaporative cooling

NaCl in sweat raises heat of vaporization-> greater heat loss than pure water

35
Q

strategies for surviving freezing temp

A

freeze tolerance (can allow tissues to freeze)

freeze avoidance (behavioural + physiological mechanism to prevent ice crystal formation)

36
Q

why is ice crystal formation an issue?
how can it be avoided?

A

points and edges can pierce membranes

crystal growth removes surrounding water, osmolarity up

avoid by preventing nucleator from forming

37
Q

how can we depress the freezing point

A

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

38
Q

diff between colligative and non-colligative cryoprotectant

A

colligative: depression of freezing point by changes in osmolarity

non-colligative: additional interactions that prevent freezing eg inhibit crystal growth

39
Q

2 mechanisms of freeze-tolerance

A

produce nucleators outside of cell (extracellular fluid freezes but intracellular fluid remains liquid)

produce intracellular solutes to counter movement of water

40
Q

in frogs, freezing is restricted to…

what does the animal do to prepare

A

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

41
Q

what are nucleating agents

A

compounds that ice can rapidly form around

42
Q

why is the cell dehydrated when part of the animal is frozen?

A

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

43
Q

what is super cooling?

A

in the absence of a nucleator, water can remain liquid below the freezing point of the fluid

44
Q

how do antifreeze macromolecules work?

A

disrupt ice crystal formation by binding to small ice crystal and preventing growth
(noncolligative)

45
Q

why do freshwater breathing fishes not really have to worry about freeze avoidance when there is water around?

A

water will freeze before tissues do

46
Q

how can polar fishes withstand water temp below freezing temp of tissues

A

anti-freeze proteins that inhibit crystal growth (vs. antifreeze mechanism in frogs promote crystal growth extracellularly)

metabolically costly to make but need very little

biol 364 (6 decks)

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