The correct option is D Organic fat
The respiratory quotient (RQ) is the ratio of CO2 produced to O2 consumed while food is being metabolized.
RQ = CO2 eliminated/O2 consumed.
The respiratory quotient for carbohydrate metabolism can be demonstrated by the chemical equation for oxidation of glucose.
C6H12O6 + 6 O2 6 CO2+ 6 H2O
Because the gas exchange in this reaction is equal, the respiratory quotient for carbohydrates is: RQ = 6 CO2 / 6 O2 = 1. Thus, option A is wrong.
The chemical composition of fats differs from that of carbohydrates in that fats contain considerably fewer oxygen atoms in proportion to atoms of carbon and hydrogen. The substrate utilization of palmitic acid is:
C16H32O2 + 23 O2 16 CO2 + 16 H2O
Thus, the RQ for palmitic acid is approximately 0.7. RQ = 16 CO2 / 23 O2 = 0.696. Thus, option B is wrong.
The respiratory quotient for protein metabolism can be demonstrated by the chemical equation for oxidation of albumin:
C72H112N18O2S + 77 O2 63 CO2 + 38 H2O + SO3 + 9 CO(NH2)2
The RQ for protein is approximately 0.8. RQ = 63 CO2/ 77O2 = 0.8. Thus, option C is wrong.
In case of organic fats, volume of CO2 given out during respiration is more than the volume of O2 used. Thus, option D is correct.