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Metabolism��

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Metabolic Rate

  • Measure of the energy produced by an organism
    • how is energy produced?
      • 1st Law of Themodynamics: energy is neither created nor destroyed, it only changes form.
      • No change in energy is 100% efficient
      • Energy is lost as heat
  • Energy changes from bond energy to heat and kinetic energy
    • Anabolic – bond-making reactions
    • Catabolic – bond-breacking reactions
    • Both can produce heat.
  • Animals can use heat in different ways

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Heat Production

  • Endotherms
    • Internal Thermoregulation
  • Ectotherms
    • Behavioral Thermoregulation

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  • Poikilotherms (heterotherms)
    • Fluctuating body temperature
  • Homeotherms
    • Constant body temperature

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  • There is no way to measure MR directly

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Direct Calorimetry

  • Measures heat produced
  • Closed system surrounded by water
  • Measure the temperature change of the water

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  • Why this system does not work
    • Can’t be completely closed system
    • Ectotherms do not produce enough heat
    • Large animals are hard to isolate

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  • Works best with small endotherms.

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Respirometry (Indirect Calorimetry)

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Respiratory Exchange Ratio

  • Respiratory Exchange Ratio (RER) = VCO2/VO2
    • on the whole animal level
    • VCO2 = the amount of CO2 produced over time
    • VO2 = the amount of O2 consumed over time
  • Respiratory quotient (RQ) = RER
    • on the cellular level
  • RER and RQ can tell us what fuel is being used for MR
    • Carbohydrates ≥ 1
    • Protein = 0.8 - 0.9
    • Lipids ≤ 0.7

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Changes in Metabolic Rate

  • Is metabolic rate constant all the time? If not why not?

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    • Temperature Change
      • TNZ – thermal neutral zone
      • BMR – basal metabolic rate
      • SMR – standard metabolic rate

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    • Eating
      • SDA – specific dynamic action

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    • Exercise/Stress
      • Increased use of ATP

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    • Body Mass

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