haya.Learning made clear
Respiratory quotient (RQ) sheet
4-mark answer frame

What is respiratory quotient? Calculate the RQ of glucose and of tripalmitin, and explain the difference.

How to lay out the answer. Follow the frame, then write it in your own words.

  1. 1 · Define in one line. RQ = volume of CO₂ released ÷ volume of O₂ consumed during respiration.
  2. 2 · Glucose. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O; RQ = 6/6 = 1.
  3. 3 · Tripalmitin (a fat). 2C₅₁H₉₈O₆ + 145O₂ → 102CO₂ + 98H₂O; RQ = 102/145 = 0.7 (rounded).
  4. 4 · Explain the difference. Fats contain little oxygen, so they need more O₂ and their RQ is less than 1. Oxygen-rich organic acids have an RQ above 1.
  5. 5 · Real life. A person's RQ falls towards 0.7 after a long fast, as the body burns stored fat.
  6. 6 · Close in one line. So RQ tells us which food is being respired.

Scoring tip: Always show the balanced equation and the fraction before the decimal answer. Say how you rounded.