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The Respiratory Quotient (RQ)
The rate of CO2 produced : The rate of O2 consumed.
C6H12O6 + 6O2 6CO2+ 6H2O RQ = 6/6 = 1.0
C18H34O2 + 25.5O2 18CO2 + 17H2O RQ = 18/25.5 = 0.7
If photosynthesis is not controlled the RQ can be negative. Therefore, RQ measurements are taken in the dark.
These measure the rates of respiration in tissues or whole organisms.
KOH or NaOH absorb CO2
As CO2 is produced in the respirometer it is absorbed
But at the same time O2 is absorbed by the organism. This may be absorbed at different rates depending upon the food being consumed.
Two experiments are needed
If glucose is used (b) will show no change (RQ = 1)
If fats are being used a reduced volume will be observed in (b) (RQ = 0.7).
If anaerobic respiration takes place an increase in volume will be observed in (b) (RQ >1)
Therefore: O2 (in) = Volume change in (a) - Volume change in (b)
Note: Ambient air pressure and temperature need to be controlled as they will also affect the volumes in the respirometer.
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