Biology · Respiration in Plants · NEET
Write the balanced equation: 2(C51H98O6) + 145 O2 to 102 CO2 + 98 H2O + energy. RQ = volume of CO2 evolved / volume of O2 consumed. Take the numbers in front of CO2 and O2: RQ = 102 / 145 = 0.703, which is rounded to 0.7. You only use the CO2 and O2 numbers, not H2O.
A fat like tripalmitin has very few oxygen atoms inside its own molecule compared to its many carbon and hydrogen atoms. To fully oxidise it, the cell must pull in extra O2 from outside. So O2 consumed (145) is more than CO2 released (102). A larger bottom number makes the ratio less than 1, so RQ = 0.7.
Glucose (C6H12O6) already carries plenty of oxygen inside it, so equal volumes of CO2 and O2 are exchanged: 6 CO2 / 6 O2 = 1. A fat carries little internal oxygen, so it needs more external O2, giving RQ less than 1. Carbohydrate = 1, fat = about 0.7, protein = about 0.9.
No. Tripalmitin is a fat (a triglyceride made of glycerol and three palmitic acid chains). Its formula C51H98O6 has 51 carbons but only 6 oxygens, which is why it behaves like a fat and gives RQ = 0.7, not 1.
No. RQ only compares CO2 evolved to O2 consumed. Water is a product but it is not part of the ratio. So for tripalmitin use only 102 (CO2) and 145 (O2), giving 102/145 = 0.7.
Respiratory Quotient (RQ) value of tripalmitin is
2(C51H98O6) + 145 O2 to 102 CO2 + 98 H2O + energy. The Respiratory Quotient (RQ) of a biomolecule used for respiration, as per the above equation would be:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The RQ of tripalmitin is 0.7. It is calculated as 102 CO2 / 145 O2 = 0.703, rounded to 0.7. This is the standard fat example given in NCERT.
2(C51H98O6) + 145 O2 to 102 CO2 + 98 H2O + energy. The coefficients 102 (CO2) and 145 (O2) are the numbers used to find RQ.
Because a fat has little oxygen inside its molecule and needs extra O2 from outside for full oxidation. More O2 is consumed (145) than CO2 released (102), so the ratio drops below 1 to 0.7.
No. NCERT states that in living organisms respiratory substrates are usually more than one, and pure fats or pure proteins are almost never used alone. Tripalmitin is used only as a teaching example to show how fat RQ is below 1.
Carbohydrate RQ = 1, fat (tripalmitin) RQ = about 0.7, and protein RQ = about 0.9. The more internal oxygen a substrate has, the closer its RQ is to 1.
