CoachThe respiratory quotient RQ is the ratio of produced to consumed, in moles. Carbohydrate gives 1.0 (six of each per glucose); fat about 0.7 (palmitate: , ), because its carbons are more reduced and need more oxygen per ; protein about 0.8. A fermenting culture releases without taking oxygen: its RQ is infinite, and a mixed culture’s RQ above 1 measures the share of fermentation. Measured on a whole animal by gas analysis, the RQ tells which fuel it is burning.
Examples
Example 15.14 (Reading an RQ)
A resting human after a carbohydrate meal: RQ 0.95, glucose burning. The same person after a night’s fast: 0.75, fat. A marathon runner at the thirtieth kilometre, glycogen gone: 0.72. A flask of yeast on glucose with a little air: RQ 4 — three quarters of its glucose is being fermented.