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BIOL 364 > Temperature 4: Mechanisms of Thermogenesis > Flashcards

Temperature 4: Mechanisms of Thermogenesis Flashcards

1
Q

how can temperature affect enzyme kinetics (2)

A
  • affects protein structure and function
  • as a result, catalytic properties of enzyme are altered
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2
Q

how can the catalytic properties of enzymes be altered by temperature (3)

A
  • changes in weak bonds affect 3D structure
  • ionization state of critical amino acids can change within the active site
  • ability of enzyme to undergo structural changes for catalysis can be altered
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3
Q

how are biochemical reactions affected by temperature (3)

A
  • accelerated at higher temperatures
  • reduced at lower temperatures
  • due to Q10 effects
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4
Q

what are Km values (2)

A
  • concentration of the substrate at which half of the active sites of the enzyme are occupied by the substrate
  • determines binding capacity/affinity of an enzyme for a given substrate
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5
Q

conservation of Km

A
  • Km values are relatively similar/conserved across animals in a variety of climates
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6
Q

how can ectotherm adapt to long-term changes in temperature

A
  • ectotherms can remodel tissues in response to long-term changes in temperature
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7
Q

ectotherm tissue remodeling: quantitative strategy (2)

A
  • changing the amount of metabolic “machinery”
  • eg. increase in the number of muscle mitochondria in low temperature
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8
Q

ectotherm tissue remodeling: qualitative strategy (2)

A
  • alter the type of metabolic “machinery”
  • eg. use different myosin isoforms in winter and summer
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9
Q

what happens to proteins at high temperatures (2)

A
  • proteins denature
  • accumulation of denatured proteins can kill the cell
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10
Q

heat shock proteins (3)

A
  • molecular chaperones
  • catalyze protein folding
  • help refold denatured proteins
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11
Q

heat shock response

A
  • increase in the levels of HSP in response to extreme temperatures
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12
Q

what is endothermy intertwined with

A
  • high metabolic rate to maintain heat production
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13
Q

thermogenesis

A
  • metabolic processes that generate heat
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14
Q

what are advantages of high body temperature (2)

A
  • faster enzyme activity speeds up all processes/systems inside body
  • organism can respond more quickly to the environment
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15
Q

what are disadvantages of high body temperature (2)

A
  • metabolically expensive
  • higher food requirement
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16
Q

what does endothermy require regulation of (2)

A
  • thermogenesis
  • heat exchange with the environment
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17
Q

how is heat produced

A
  • as a by-product of metabolic processes
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18
Q

what metabolic processes produce heat (3)

A
  • energy metabolism
  • digestion
  • muscle activity
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19
Q

both endotherms and ectotherms produce metabolic heat, why do endotherms have high body temperature (2)

A
  • only endotherms have ability to retain enough heat to elevate body temperature above environmental temperature
  • endotherms possess futile cycles
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20
Q

futile cycles

A
  • metabolic reactions which sole purpose is to produce heat
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21
Q

shivering thermogenesis: organism (2)

A
  • birds
  • mammals
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22
Q

shivering thermogenesis (2)

A
  • uncoordinated myofiber contraction
  • results in no gross muscle contraction
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23
Q

shivering thermogenesis: effective time frame

A
  • works for short periods of time
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24
Q

why does shivering thermogenesis only work for short periods of time

A
  • muscles are rapidly depleted of nutrients and become exhausted
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25
Q

when is thermogenesis used in insects (2)

A
  • heat production in insects prior to flight
  • insects spend time contracting muscles to generate heat
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26
Q

mechanism of heat production in insects

A
  • carbohydrate metabolism in flight muscles
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27
Q

heat production in insects: flight muscles

A
  • antagonistic flight muscles contract simultaneously
  • expend energy and produce heat without movement
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28
Q

heat production in insects: wing movement

A
  • frequency and orientation of the wings are controlled to contract, without generating lift
29
Q

what are ion gradients used for

A
  • membrane proteins use electrochemical energy from ion gradients to drive transport and biosynthesis
30
Q

what is done to maintain ion gradients

A
  • ions must be continually pumped because ions leak across membranes
31
Q

how does ion movement contribute to thermogenesis

A
  • ion-pumping membrane proteins produce heat
32
Q

how are the plasma membranes different between endotherms and ectotherms (2)

A
  • endotherms have leaker plasma membranes than ectotherms
  • endotherms have increased thermogenesis due to ion pumping
33
Q

brown adipose tissue (2)

A
  • used for shivering thermogenesis
  • important for thermogenesis in small mammals and newborns that live in relatively cold environments
34
Q

where is brown adipose tissue located

A
  • near back and shoulder regions
35
Q

how does brown adipose tissue differ from white adipocytes (2)

A
  • higher levels of mitochondria (making it brown)
  • produces thermogenin protein
36
Q

what does thermogenin do (3)

A
  • inserts into mitochondrial membranes
  • uncouples mitochondrial proton pumping from ATP synthesis
  • increases leakiness of membrane, making it harder to maintain proton gradients
37
Q

what are the characteristics of mitochondria with thermogenin (2)

A
  • high rate of fatty acid oxidation
  • more energy is release as heat
38
Q

internal thermostat: mammals (2)

A
  • information from central and peripheral thermal sensors is integrated in the hypothalamus
  • hypothalamus sends signals to the body to alter rates of heat production and dissipation
39
Q

internal thermostat: birds

A
  • thermostat located in the spinal cord
40
Q

how can hair/feathers help control heat

A
  • piloerection
41
Q

piloerection (3)

A
  • hair and feathers act as insulation and fluff up when it is cold
  • hair and feathers are pulled perpendicular by smooth muscles (erector muscles) attached at their base
  • reduces thermal conductivity
42
Q

what is the efficiency of insulation by piloerection determined by

A
  • the thickness of the hair/feathers
43
Q

how can blood vessels help control heat

A
  • vasomotor response
44
Q

vasomotor response

A
  • altering blood flow to the body surface can change the rate of heat exchange
45
Q

vasomotor response: cold ambient temperature (2)

A
  • skin arteriole constricts and AV shunt dilates
  • blood is directed away from the skin to minimize heat loss from blood at the skin
46
Q

vasomotor response: hot ambient temperature (2)

A
  • skin arteriole dilates and AV shunt constricts
  • blood is directly toward to skin surface to maximize heat loss from blood
47
Q

vasomotor response: normal body temperature (2)

A
  • maintains tonic constriction of arterioles
  • reduces unnecessary loss of heat
48
Q

vasomotor response: mechanism (2)

A
  • sympathetic nervous system maintains constriction of arterioles
  • mediated by α adrenergic signals
49
Q

countercurrent heat exchangers (2)

A
  • transfer thermal energy from warm arterial blood to cooler venous blood at surfaces where heat exchange can occur
  • retains heat away from the heat exchanger surface
50
Q

nasal countercurrent exchange (3)

A
  • incoming air is humidifies and heated
  • outgoing air is condensed and cooled
  • recycles and conserves water while preventing heat loss
51
Q

which animals use sweating

A
  • large animals with low SA:V ratio
52
Q

how does sweating decrease body temperature

A
  • evaporative cooling
53
Q

how does NaCl content in sweat help decrease body temperature (2)

A
  • raises heat of evaporation
  • greater heat loss than evaporation of pure water
54
Q

what is sweating controlled by (2)

A
  • hypothalamus
  • sympathetic stimulation of sweat glands
55
Q

how and why does NaCl content change in sweat (2)

A
  • NaCl content decreases in sweat during long exposure to heat
  • minimizes ionic and osmotic problems
56
Q

why is the respiratory surface good at heat loss (4)

A
  • properties that make a respiratory surface good at gas exchange also enhance heat loss
  • high vascularity
  • moist surface
  • high airflow
57
Q

how can respiration be used to enhance heat loss (3)

A
  • rapid ventilation increases heat loss by convection and evaporation
58
Q

respiration to enhance heat loss: mammals

A
  • panting
59
Q

how can respiration be used to enhance heat loss: birds

A
  • gular fluttering
60
Q

how does panting results in heat loss (2)

A
  • mouth lacks nasal countercurrent exchange system for heat conservation
  • mouth is intentionally used to dump body heat
61
Q

how does panting avoid affecting gas transport over the ventilatory surface (3)

A
  • increased breathing frequency results in small volume of air moving in and out of animal
  • each breath ventilates dead space more than alveolar space
  • high air flow occurs over nasal mucosa, tongue and other moist surfaces to increase evaporative heat loss without altering gas transport conditions
62
Q

what is relaxed endothermy (2)

A
  • temporarily lowering basal metabolic rate (BMR) to achieve a hypometabolic state
  • relaxes and resets body temperature
63
Q

relaxed endothermy types (2)

A
  • torpor
  • hibernation
64
Q

relaxed endothermy: torpor

A
  • decrease in body temperature by ~10C to decrease metabolic rate
65
Q

relaxed endothermy: what animals practice torpor (2)

A
  • small birds
  • small mammals
66
Q

relaxed endothermy: hibernation

A
  • decrease in body temperature by ~20C to decrease metabolic rate
67
Q

relaxed endothermy: what animals practice hiberation

A
  • small and large mammals
68
Q

what is the advantage of relaxed endothermy

A
  • saves fuel when food supply becomes limited

BIOL 364 (44 decks)

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