Topic 65 - Calorimetryc methods, the definition and importance of the respiratory quotient Flashcards

1
Q

Words to include in calorimetryc methods

A
  • Direct calorimetry
    • Method of Lavoiser and Laplace
    • Complex direct caloirmetry
    • Compensation calorimetry
    • Gradient calorimetry
  • Indirect calorimetry
    • Open system
    • Closed system

Direct calorimetry

  • Method of Lavoiser and Laplace
    • Chamber
      • Animal
      • Surrounded by ice
    • Heat generation
      • Amount of melted ice
    • Expired air and evaporation (ø measured)
  • Complex direct calorimetry
    • Emission of water vapor
    • Heat isolated chamber
    • Adiabatic calorimeter
    • Total heat production
      • Water evaporated
        • Increase in weight (calculated)
      • Water absorbing substances
  • Compensation calorimeter
    • 2 chambers of identical thermal capacity
      • Constant temperature
      • 1 chamber: animal
      • 1 chamber: electric bulb of known output
    • Animal heats up chamber = bulb warms up the other chamber for equal temperatur
    • 1J = 1Ws (Watt-secundum)
  • Gradient calorimeter
    • Double walled chamber
      • Inner wall: heat conducter
      • Outer wall: constant temperature
    • Heat difference between wall
      • Amount of heat dissipated

Indirect calorimetry

  • Open system
    • Environmental / atmospheric O2 inspired
    • Expired air measured
    • Douglas bag
      • Gas-storing bag
      • Exhalation
      • Inhalation
  • Closed system
    • No atmospheric O2 inhaled
    • Oxygen added to system
    • Amount of consumed O2

Complex indirect and direct calorimetry

  • Atwar-Rose Respiratory Calorimetry
  • Closed, heat-isolated chamber
    • Measure water temperature ↑
    • Velocity of water outflow
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2
Q

Words to include in respiratory quotient (RQ)

A
  • RQ = CO2 [vol./time] / O2 [vol./time]
  • Respiratory quotient = respiratory exchange rate
  • Range of RQ: 0.7-1.0
    • Hyperventilation: RQ ↑ (2.0)
    • Metabolic acidosis: RQ ↑
    • After exercise: RQ ↓ (0.5)
    • Fattening: RQ > 1
    • Starving RQ < 0.5
  • Oxidized carbohydrate, protein and fat:
    • Expired CO2
    • Inspired O2
  • Qualitiative composition of energy sources
  • Chemical reaction of metabolism
    • Stoichiometric
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3
Q

Calorimetryc methods

Name the different calorimetryc methods

A
  1. Direct calorimetry
    • Method of Lavoiser and Laplace
    • Complex direct calorimetry
    • Compensation calorimetry
    • Gradient calorimetry
  2. Indirect calorimetry
    • Open system
    • Closed system
  3. Complex indirect and direct calorimetry (Atwater-Rose respiratory calorimeter)
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4
Q

Calorimetryc methods

Direct calorimetry

A

​Method of Lavoiser & Laplace

  • Chamber containing the animal surrounded by ice
    • The amount of melting ice and the water being produced was used to estimate heat generation
  • Disadvatages:__​
    • Expired air and evaporation off the body are not measured
    • High humidity in the chamber

Complex direct calorimetry

  • Emission of water vapor from the body
  • Water of known temperature enters the outer casing of the heat isolated chamber (containing the animal)
  • Heat emitted from the animal heats up the water
    • Temperature of the water leaving the casing is measured
    • From this value and velocity of flow, heat production can be calculated (adiabatic calorimeter)

Compensation calorimeter

  • 2 chambers of identical thermal capacity are connected
    • Chamber 1: animal inside
    • Chamber 2: electric bulb of known output inside
  • Animal heats up tis chamger → the bulb will warm up its chamber to keep the temperature equal in both chambers
  • Energy used by the bulb = output of heat produced by animal
  • 1 J = 1 Ws (watt-secundum)

Gradient calorimeter

  • Double walled chamber
    • Inner wall: good heat conduction
    • Outer wall: constant temperature
  • The heat difference between the two walls is measured to calculate the amount of heat dissipated
  • It detects the heat loss occuring by means of:
    • Radiation
    • Conduction
    • Convection
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5
Q

Calorimetryc methods

Indirect calorimetry

A

Open system

  • Environmental / atmospheric O2 inspired
  • Expired air is measured
  • Douglas bag
    • Gas storing bag
    • Exhalation
    • Inhalation

Closed system

  1. ​On atmospheric O2 inhaled
  2. Oxygen is added to the system
  3. Indicator directly shows amount of consumed O2
  • Advantage of indirect calorimetry:
    • Animal can move freely in its natural environment
  • Disadvantage of indirect calorimetry:
    • Restricted ability to measure the O2-dependant energy production only
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6
Q

Calorimetryc methods

Complex indirect and direct calorimetry

A
  • Atwar-Rose respiratory calorimeter
  • The experimental animal is placed into a closed, heat-isolated chamber. The degree of heat production of the animal can be calculated from data collected by measuring:
    • Water temperature ↑
    • Velocityof thewater outflow
  • O2 consumption and CO2 production of the animal can also be determined
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7
Q

Respiratory quotient

A
  • Respiratory quotient = respiratory exchange rate
  • Definition: the volume of production of CO2 within a time unit divided by the volume of consumed O2 during the same period
  • Range of RQ: 0.7 - 1.0
    • ​Hyperventilation: RQ ↑ (2.0)
    • Metabolic acidosis: RQ
    • After exercise: RQ ↓ (0.5) - paying back of O2 debt
    • Fattening: RQ > 1
    • Starving: RQ < 0.5
  • The amount of oxidized carbohydrate, protein and fat can be approximated from the amounts of:
    • Expired CO2
    • Inspired O2
    • Nitrogen excretedin theurine
  • RQ values can provide information about the qualitative composition of energy sources (carbohydrate, protein & fat)
  • Chemical reactions of metabolism are stoichiometric
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