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S295 The Biology of Survival > Topic 7 Surviving the cold > Flashcards

Topic 7 Surviving the cold Flashcards

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1
Q

What is thermoregulation?

A

Thermoregulation is a process by which organisms maintain their internal temperature within their optimum range for survival, achieved by constantly balancing heat loss with head gain.

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2
Q

How might enzyme structural changes influence metabolic reactions?

A

They may speed up or slow down reactions.

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3
Q

What is torpor?

A

A state of controlled lowered body temperature and metabolic rate.

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4
Q

Define endothermic in terms of heat source.

A

Controls temperature through internal means such as muscle shivering or increased metabolism.

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5
Q

Define ectothermic in terms of heat source.

A

Gains heat from external sources.

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6
Q

Define homeothermic.

A

Maintains a stable temperature irrespective of their external environment.

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7
Q

Define poikilothermic.

A

The organism’s temperature is highly variable and tends to respond to that of its environment.

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8
Q

What features do small animals have that put them at a disadvantage in relation to thermoregulation?

A
  • Large surface area to volume ratios resulting in high rates of heat loss.
  • High basal metabolic rates (BMR)
  • Reduced capacity for internal heat storage
  • Minimal insulation in the form of adipose tissue.
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9
Q

Define heterothermy

A

The regulation of body temperature within a limited range (not as narrow as homeothermy), independently of ambient temperature by switching between strategies and utilising torpor.

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10
Q

What are some triggers that may trigger torpor?

A

When an animal is:
* Young
* small
* cold
* in a prolonged state of hunger

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11
Q

What is the pattern of development of thermoregulatory strategies in placentals?

A
  1. Poikilothermy
  2. Homeothermy
  3. Heterothermy
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12
Q

What is the pattern of development of thermoregulatory strategies in birds and marsupials?

A
  1. Poikilothermy
  2. Heterothermy
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13
Q

What is thermogenesis?

A

The process of producing heat in animal body tissues, though also occurs in some plants.

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14
Q

How does circulation of animals change in response to cold conditions?

A

The circulation shuts down in the peripheries and withdraws into the core of the body and brain, setting up a temperature gradient or thermocline.

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15
Q

What are some features that enable animals to live on ice flows or in cold waters to avoid experiencing damage to their extremities?

A
  • Waterproofing
  • Isolation
  • Thickened skin
  • Natural antifreeze compounds
  • Specialised circulatory features
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16
Q

Define metabolic rate.

A

An organisms energy utilisation per time - most basic unit used is watts (W).

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17
Q

What is the sympathetic nervous system?

A

Part of the autonomic nervous system which controls many involuntary processes.

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18
Q

What is the autonomic nervous system?

A

The part of the nervous system that controls involuntary actions of many systems. Comprises the sympathetic and parasymptathetic systems.

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19
Q

How may adaption to cold be gained?

A
  • May be inherited
  • May be acquired within an organism’s lifetime by acclimation
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20
Q

What are some physiological responses to cold?

A
  • Insulative
  • Circulatory adjustments to decreased skin temperature
  • Metabolic
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21
Q

What are some short-term changes in response to cold?

A
  • Shivering
  • Behavioural adjustments
  • Accumulating energy stores
  • Torpor, hibernation, dormancy
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22
Q

What are some longer-term changes in response to the cold?

A
  • Insulation
  • Circulatory changes
  • Heat generation by specialised metabolic processes
  • Non shivering thermogenesis
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23
Q

What is countercurrent heat exchange?

A

A countercurrent exchanger consists of a pair of channels lying in close proximity that contains fluids or gases flowing in opposite directions e.g., where heat loss from the body core to the extremities is minimised by heat transfer between adjacent blood vessels before reaching the outer body surfaces.

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24
Q

In mammals and birds, how is air warmed before it reaches the lung?

A

By the nose.

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25
Q

What is non-shivering thermogenesis (NST)?

A

Thermogenesis in brown adipose tissue. Strictly, includes all metabolic thermogenesis except that produced by shivering.

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26
Q

In what individuals is BAT more active?

A

Neonates, small animals, and animals that hibernate.

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27
Q

What are the three main macromolecules and what are their roles?

A
  • Carbohydrates - main and immediate energy source for the body
  • Lipids - rich source of energy, key components of cell membranes, some signalling molecules
  • Proteins - numoerous processes, any dietry proteins consumed in excess of those needed for growth or maintenance can also be used to provide energy for other activities such as respiration
28
Q

What are the lipids that store energy called and what are they made up from?

A

Triacyglycerols (TAGs) - made up of three fatty acid molecules combined with one molecule of glycerol. The chains tend to be different lengths, with longer chains (more C-C bonds) storing more energy.

29
Q

What purpose do TAGs in seeds serve?

A

To provide a store of energy needed to allow growth to resume when the seed germinates.

30
Q

What is lipolysis?

A

The splitting of triacylglycerols into free fatty acids and glycerol by the action of a lipase.

31
Q

Quantitively, which energy store is most important in humans?

A

Adipose tissue TAGs

32
Q

What are the two types of adipose tissue?

A
  • White adipose tissue (WAT)
  • Brown adipose tissue (BAT)
33
Q

What kind of organisms is white adipose tissue exclusive to?

A

Vertebrates

34
Q

What kind of tissue is white adipose tissue primarily?

A

Storage and secretory

35
Q

What type of cells make up white adipose tissue?

A

white adipocytes

36
Q

What is the composition of a mature white adipocyte?

A
  • Single large lipid droplet
  • Relatively small nuclei squeexed against cell membrane
  • Small mitochondria (too small to be seen with a light microscope)
  • Network of extracellular collagen
37
Q

What is white adipose tissue expansion in humans and rats due to?

A

Adipocyte enlargement (not increased cells), which in turn is due to the quantity of TAGs stored within them.

38
Q

What organisms is Brown adipose tissue (BAT) exclusive to?

A

Mammals

39
Q

What is the function of brown adipose tissue (BAT)?

A

A specialised tissue adapted to generate additional heat when heat released as a by-product of other metabolic processes is not enough to maintain body temperature.

40
Q

What cells are brown adipose tissue composed of?

A

Brown adipocytes

41
Q

What are some differences between brown and white adipocytes?

A
  • Brown adipocytes are smaller than white adipocytes
  • Brown adipocytes contain TAGs in multiple small droplets, rather than one large one.
42
Q

What is the composition of a brown adipocyte?

A
  • Smaller than white adipocytes
  • Contain multiple small droplets of TAGs
  • Small mitochondria too small to be seen in light microscope.
43
Q

What is ‘standard metabolic rate’?

A

Environmental temperature changes affect body temperature and the metabolic rate of an ectotherm, so the minimum metabolic rate will be different at various temperatures and is called its standard metabolic rate (at a specified temperature).

44
Q

Name three forms in which nitrogenous waste can be excreted as.

A
  • Ammonia
  • Urea
  • Uric acid
45
Q

Ammonia generated by the break down of what?

A

Proteins and nucleic acids

46
Q

Why is ammonia potentially toxic to cells?

A

It raises cellular pH

47
Q

What can ammonia be converted to?

A

Urea or uric acid

48
Q

What nitrogenous waste is produced by most aquatic animals, including most bony fishes?

A

Ammonia

49
Q

What nitrogenous waste is produced by mammals, most amphibians, sharks, and some bony fishes?

A

Urea

50
Q

What nitrogenous waste is produced by birds, reptiles, insects, and land snails?

A

Uric acid.

51
Q

Why would meat-eating predators extrete relatively high levels of nitrogenous waste?

A

As the food they consume (meat) are high in protein.

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52
Q

How are each of the nitrogenous waste forms excreted in terms of form?

A
  • Uric acid - paste like
  • Urea - dissolved in water
  • Ammonia - dissolved in water
53
Q

Define osmolarity

A

Measure of the solute concentration of a solution

54
Q

List the properties of ammonia (Toxicity, water solubility, water requirement, physical form, energetic costs, and habitat)

A
  • Very toxic
  • dissolves in water
  • +++ high water requirement
  • Liquid
    • low energetic costs
  • aquatic species
55
Q

List the properties of Urea (Toxicity, water solubility, water requirement, physical form, energetic costs, and habitat)

A
  • Lower toxicity
  • dissolves in water
  • ++ medium water requirement
  • Liquid
  • ++ medium energy costs
  • Land dwelling animals with access to water or marine species that lose water to the environment
56
Q

List the properties of uric acid (Toxicity, water solubility, water requirement, physical form, energetic costs, and habitat)

A
  • Relatively non-toxic
  • Does not readily dissolve in water
    • low water requirement
  • Paste
  • +++ high energy costs
  • Land dwelling animals with restricted access to water
57
Q

What is the particularly defining feature of true hibernaton?

A

Hibernators arouse themselves throughout the hibernation period unrelated to the surrounding temperature. Thus, on multiple occasions during hibernation, their metabolic rate and temperature increase to approximately normal levels, before dropping again - they also excrete urine and faeces at these times.

58
Q

How is BAT involved in the arousal of hibernators?

A

BAT oxidises fatty acids to rapidly generate heat.

59
Q

Where are BAT deposites generally found on small mammals?

A

On their backs, between their shoulder blades, and close to internal organs

60
Q

What are some of the different ways in which trophic positions can differ for the same species?

A

May be temporal variation (over time), or spatial variation (occuring in different places)

61
Q

What is the ‘trophic match-mismatch hypothesis’?

A

Suggests that the reproduction of predators is more successful at times when this is matched with peak prey availability. It attempts to explain variation within a predator population by relating its phenology to prey species at the next trophic lower level. Thus it is a measure of reproductive success due to how well the phenology of the prey is matched by and able to meet the requirements of its predator.

62
Q

What is a substrate cycle?

A

Takes place when two metabolic pathways run in opposite directions simulateously, catalysed by different enzymes, dissipating energy in the form of heat.

63
Q

What are the four stages in the oxidation of glucose in aerobic respiration and where in the cell do they take place?

A
  1. Glycolysis - cytosol
  2. Link reaction - mitochondrial matrix
  3. TCA (Krebs) cycle - mitochondrial matrix
  4. ETC and oxidative phosphorylation - inner mitochondrial membrane
64
Q

What protein do Brown adipose tissue cells possess that allow for uncoupling between the ETC and ATP synthesis?

A

UCP1 in the inner mitochondrial membrane that provides a route for protons to move down their concewntration gradient from the outside to the inside of the inner mitochondrial membrane without ATP being synthesised.

65
Q

List the processes that occur in BAT after activation by the neurostransmitter noradrenaline.

A
  • Activation of lipase which cleaves stored TAGs to release fatty acids
  • Division and differentiation of BAT cells, resulting in increased mass of tissue available for heat generation
  • Increase in the number of mitochondria in the cells
  • Increase in the folding of mitochondrial cristae
  • Increase in the synthesis of the protein UCP1
  • Increase in tissue perfusion to increase supply of oxygen and nutrients
  • Inhibition of apoptosis in brown adipocytes
66
Q

How can thermogenesis in BAT be switched off?

A

By nucleotides (e.g., ATP) which bind to UCP1 and prevent it from allowing the passage of protons under normal temperature conditions.

67
Q

How is thermogenesis in BAT switched on?

A

By the presence of an increased concentration of fatty acids that displace the nucleotide and allows UCP1 to transport protons across the inner mitochondrial membrane, generating heat.

S295 The Biology of Survival (13 decks)

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