R ESPIRATORY Q UOTIENT

R ESPIRATORY Q UOTIENT Let us now look at another aspect of respiration. As you know, during aerobic respiration, O is consumed and CO is released. The ratio of the volume of CO evolved to the volume of O consumed in respiration is called the respiratory quotient (RQ) or respiratory ratio. RQ volumeof CO evolved volumeof O consumed The respiratory quotient depends upon the type of respiratory substrate used during respiration. When carbohydrates are used as substrate and are completely oxidised, the RQ will be , because equal amounts of CO and O are evolved and consumed, respectively, as shown in the equation below : Figure . Interrelationship among metabolic pathways showing respiration mediated breakdown of different organic molecules to CO and H C H O H O Energy → RQ . When fats are used in respiration, the RQ is less than . Calculations for a fatty acid, tripalmitin, if used as a substrate is shown: ( ) C H O H O energy → Tripalmitin RQ . When proteins are respiratory substrates the ratio would be about . . What is important to recognise is that in living organisms respiratory substrates are often more than one; pure proteins or fats are never used as respiratory substrates.