Respiratory Quotient (R.Q). The ratio of volume of CO2 evolved to the volume of oxygen consumed per unit time per unit weight. R.Q. indicates the type of respiratory substrate being used and type of respiration being performed R.Q. value is one for aerobic respiration of glucose; more than one for organic acids (e.g. 1.3 for malic acid and 1.14 for succinic acid) less than one for fats (0.7) and proteins (0.85); infinity for anaeobic respiration (as no oxygen is used). It can be measured by respiirometer.