Respiratory quotient

RQ is dependent on the type of substrate metabolized, it means that varies from rest to exercise. Here, the RQ is in the diet with carbohydrates 1.0 ( stoichiometric amount of carbon and oxygen in carbohydrate are the same), in the case of proteins and fats 0.7 0.81. The average Central European RQ is 0.82.

For muscle work from the RQ assumptions about the metabolic state and the metabolized energy sources - are derived - essentially, fats or carbohydrates. From a value such as the above-mentioned 0.82 can therefore be concluded that a composition of metabolized energy source, were at the burned in roughly equal parts fat and carbohydrates.

In severe physical stress in spiroergometry a RQ > 1.1 is considered a sign of exertion of the subject.

In addition, the RQ reached only in special cases 1: Animal feeding so many carbohydrates are fed that they must be converted into fats in order to save it. Here fats have a different C / O ratio, which endogenously O2 is released, so less O2 must be absorbed through the lungs ( CO2/O2 > 1). In juveniles also much material conversion is operated because of the growth processes, with the result that even here the stoichiometry changes, which O2 is endogenously released and thus reduces the absorbed by breathing O2. In both cases, an alternative hypothesis states that there is no endogenous O2 produced, but only water is free and therefore relative CO2 emissions is increased, which has the same effect on the RQ.

Determined this value is by indirect calorimetry, in the context of Spiroergometrien. When measuring a mouth and nose tightly covering mask must be worn so that from the one - and exhaled air continuously ( breath-by -breath ) can be the difference in the concentration of the above -mentioned gases for known stable concentration in the ambient air measured.

In plants, in principle, the same applies, except that the RQ in different tissues fails completely different. In photosynthetically inactive cells, it is basically the same as in animals ( cellular respiration ), but the RQ is in photosynthetically active cells absolutely the type of plant ( C3, C4, CAM ) and the situational gas exchange -dependent ( stoma opening determined by partial pressure of CO2 ), because any photorespiration could occur.

Swell

Collaz, "Metabolic physiology of animals," Herder- Verlag ( 1979)

• Breathing