Simulation · Biology · Class 11

The respiratory quotient

From the lesson Respiratory quotient in Respiration in Plants. Change the values and watch what happens.

The idea behind it

NCERT §12.7

The respiratory quotient (RQ), also called respiratory ratio, is the volume of CO₂ evolved divided by the volume of O₂ consumed in respiration.
RQ depends on which substrate is being respired.
Carbohydrates completely oxidised give RQ = 1: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy, so RQ = 6CO₂ / 6O₂ = 1.0.
Fats give RQ below 1. For tripalmitin, 2(C₅₁H₉₈O₆) + 145O₂ → 102CO₂ + 98H₂O + energy, so RQ = 102CO₂ / 145O₂ = 0.7.
Proteins as substrate give an RQ of about 0.9.
In living organisms more than one substrate is usually respired at a time; pure proteins or pure fats are never the only substrate.

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