Cellular Respiration and Metabolic Rate

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Cellular Respiration and Metabolic Rate
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Equation for Cellular Respiration

• C6H12O6 6O2 -gt 6CO2 6H20 heat (energy)

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Important Points

• Cellular Respiration yields approximately 32-38
  ATP
• 02 is an electron acceptor in the electron
  transport chain. It picks up two hydrogen ions
  and electrons to form water.

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What is the relationship between Plants and
Animals?
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Predictions/ Demonstration

• Which enclosure should stop first?
• Which enclosure is the perfect situation?
• Test your predictionsone set-up of 4
  enclosures/table.

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Metabolic Rate

• The rate of energy use by an organism is called
  the metabolic rate (MR).
• Metabolic rate is measured in units of
  kilocalories

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How to measure Metabolic Rate

• Production of heat measures MR directly
• Rate of Oxygen consumption measures MR indirectly
• Oxygen uptake and metabolic heat production has
  been measured to be on average about 4.8
  kcal/liter 02

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Many factors affect MR

• Physiological energy use e.g. Exercise During
  exercise a human can double MR.
• Stress
• Temperature
• Body size- Larger Organisms have a higher MR than
  smaller ones if all other things are the same

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MR increases more slowly than body mass- Doubling
body mass increases MR only 68
Total MR in Mammals 70W0.75
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The relationship is linear on log axes
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Mass Specific MR MR per unit body mass decreases
with mass-
a gram of mouse uses energy 25X faster than a
gram of elephant.
mass-specific MR 70W -0.25
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The relationship is linear on log axes
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Mass-specific MR of insects 30W 0.25
mammals
insects
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Kleibers Rule

• Smaller Organisms have higher mass-specific MR

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Measuring MR Measure the rate of O2 consumption
calculate MR Volumetric respirometry Method for
measuring the volume of oxygen consumed.
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Todays Lab- Test Kleibers rule by measuring MR
in two species that differ 10X in body
mass Tenebrio Zoophobas(regular mealworms and
king mealworms)
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Closed chamber respirometer in water bath KOH
absorbs the CO2 released by respiration.Worms
consume O2, decreasing gas volume in the chamber.
Water enters pipette, showing volume
change. Syringe of air is used to adjust volume
in chamber.
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Ideal Gas Law Describes the behavior of air under
normal conditions of temperature and pressure. V
nRT P V volume P pressure n
number of molecules R gas constant T
temperature oK Point any temperature or
pressure change will change the volume and
obscure the rate of oxygen consumption.
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Start at 0.9 ml
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Tips A control respirometer is run alongside the
test respirometers- the same but without any
animals Any change in volume of the control is
subtracted from the test results. Give
temperature time to equilibrate- let the
respirometers remain in the bath with the
pipettes up (out of the water) for at least 10
minutes before rolling the respirometer to
immerse the tips.
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Cautions No water in the chambers! KOH makes a
caustic solution if it gets wet. A dry worm is a
happy worm. Dont suffocate them- tip the pipette
up after each run and use the syringe to eject
the water from the pipette. Then draw fresh air
into the chamber. When finished- expel water from
the pipette before pulling the plug. (Otherwise
water in the pipette will be sucked into the
chamber).
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Hold vertical to drain- eject the water and blot
the tip