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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
when is thermogenesis used in insects (2)
- heat production in insects prior to flight - insects spend time contracting muscles to generate heat
26
mechanism of heat production in insects
- carbohydrate metabolism in flight muscles
27
heat production in insects: flight muscles
- antagonistic flight muscles contract simultaneously - expend energy and produce heat without movement
28
heat production in insects: wing movement
- frequency and orientation of the wings are controlled to contract, without generating lift
29
what are ion gradients used for
- membrane proteins use electrochemical energy from ion gradients to drive transport and biosynthesis
30
what is done to maintain ion gradients
- ions must be continually pumped because ions leak across membranes
31
how does ion movement contribute to thermogenesis
- ion-pumping membrane proteins produce heat
32
how are the plasma membranes different between endotherms and ectotherms (2)
- endotherms have leaker plasma membranes than ectotherms - endotherms have increased thermogenesis due to ion pumping
33
brown adipose tissue (2)
- used for shivering thermogenesis - important for thermogenesis in small mammals and newborns that live in relatively cold environments
34
where is brown adipose tissue located
- near back and shoulder regions
35
how does brown adipose tissue differ from white adipocytes (2)
- higher levels of mitochondria (making it brown) - produces thermogenin protein
36
what does thermogenin do (3)
- inserts into mitochondrial membranes - uncouples mitochondrial proton pumping from ATP synthesis - increases leakiness of membrane, making it harder to maintain proton gradients
37
what are the characteristics of mitochondria with thermogenin (2)
- high rate of fatty acid oxidation - more energy is release as heat
38
internal thermostat: mammals (2)
- 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
internal thermostat: birds
- thermostat located in the spinal cord
40
how can hair/feathers help control heat
- piloerection
41
piloerection (3)
- 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
what is the efficiency of insulation by piloerection determined by
- the thickness of the hair/feathers
43
how can blood vessels help control heat
- vasomotor response
44
vasomotor response
- altering blood flow to the body surface can change the rate of heat exchange
45
vasomotor response: cold ambient temperature (2)
- skin arteriole constricts and AV shunt dilates - blood is directed away from the skin to minimize heat loss from blood at the skin
46
vasomotor response: hot ambient temperature (2)
- skin arteriole dilates and AV shunt constricts - blood is directly toward to skin surface to maximize heat loss from blood
47
vasomotor response: normal body temperature (2)
- maintains tonic constriction of arterioles - reduces unnecessary loss of heat
48
vasomotor response: mechanism (2)
- sympathetic nervous system maintains constriction of arterioles - mediated by α adrenergic signals
49
countercurrent heat exchangers (2)
- 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
nasal countercurrent exchange (3)
- incoming air is humidifies and heated - outgoing air is condensed and cooled - recycles and conserves water while preventing heat loss
51
which animals use sweating
- large animals with low SA:V ratio
52
how does sweating decrease body temperature
- evaporative cooling
53
how does NaCl content in sweat help decrease body temperature (2)
- raises heat of evaporation - greater heat loss than evaporation of pure water
54
what is sweating controlled by (2)
- hypothalamus - sympathetic stimulation of sweat glands
55
how and why does NaCl content change in sweat (2)
- NaCl content decreases in sweat during long exposure to heat - minimizes ionic and osmotic problems
56
why is the respiratory surface good at heat loss (4)
- properties that make a respiratory surface good at gas exchange also enhance heat loss - high vascularity - moist surface - high airflow
57
how can respiration be used to enhance heat loss (3)
- rapid ventilation increases heat loss by convection and evaporation
58
respiration to enhance heat loss: mammals
- panting
59
how can respiration be used to enhance heat loss: birds
- gular fluttering
60
how does panting results in heat loss (2)
- mouth lacks nasal countercurrent exchange system for heat conservation - mouth is intentionally used to dump body heat
61
how does panting avoid affecting gas transport over the ventilatory surface (3)
- 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
what is relaxed endothermy (2)
- temporarily lowering basal metabolic rate (BMR) to achieve a hypometabolic state - relaxes and resets body temperature
63
relaxed endothermy types (2)
- torpor - hibernation
64
relaxed endothermy: torpor
- decrease in body temperature by ~10C to decrease metabolic rate
65
relaxed endothermy: what animals practice torpor (2)
- small birds - small mammals
66
relaxed endothermy: hibernation
- decrease in body temperature by ~20C to decrease metabolic rate
67
relaxed endothermy: what animals practice hiberation
- small and large mammals
68
what is the advantage of relaxed endothermy
- saves fuel when food supply becomes limited

BIOL 364 (44 decks)

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