Lesson 5.2.2c

5.2.2c Energy values and the respiratory quotient Quiz: OCR Biology, Unit 6

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 5.2.2c, Energy values and the respiratory quotient: 20 multiple choice questions for the OCR Biology (H020), Unit 6: Energy for biological processes, written with Revision Ninja.

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The 20 questions

  1. Which respiratory substrate releases the most energy per gram?

    • Water
    • Proteins
    • Carbohydrates
    • Lipids

  2. How is the respiratory quotient (RQ) calculated from gas exchange measurements?

    • CO2 produced x O2 used
    • O2 used / CO2 produced
    • CO2 produced + O2 used
    • CO2 produced / O2 used

  3. What is the RQ when carbohydrate is the respiratory substrate?

    • 1.5
    • 0.9
    • 1.0
    • 0.7

  4. What is the approximate RQ when fat is the respiratory substrate?

    • 0.7
    • 0.9
    • 1.0
    • 0.5

  5. Why do lipids release more energy per gram than carbohydrates during aerobic respiration?

    • More phosphate groups
    • Fewer carbon-hydrogen bonds
    • More hydrogen atoms
    • More oxygen atoms

  6. When proteins are used as a respiratory substrate in mammals, what is the main nitrogen-containing excretory product?

    • Lactate
    • Ethanol
    • Glycogen
    • Urea

  7. How does the energy value of lipids compare to that of carbohydrates per gram?

    • Approximately equal
    • Approximately half
    • Four times greater
    • Approximately double

  8. An organism consumes 30 cm3 of oxygen and produces 24 cm3 of carbon dioxide. What is its RQ?

    • 0.8
    • 1.0
    • 0.6
    • 1.25

  9. Which respiratory substrate is being broken down if an organism exhibits an RQ of 1.0?

    • Protein
    • Nucleic acid
    • Carbohydrate
    • Lipid

  10. Which RQ value indicates the highest proportion of oxygen consumed per carbon dioxide released?

    • 0.5
    • 0.9
    • 1.0
    • 0.7

  11. A respirometer has soda lime that absorbs carbon dioxide. The syringe moves 1.2 cm3 in 10 minutes. What does this volume change measure?

    • Oxygen consumed
    • Ethanol produced
    • Total gas volume
    • Carbon dioxide produced

  12. A 10 g sample of fat yields about 390 kJ, while 10 g of glucose yields about 160 kJ. What is the approximate energy ratio of fat to glucose?

    • About 2.4 to 1
    • About 4 to 1
    • About 1 to 1
    • About 0.4 to 1

  13. Which respiratory substrate releases the greatest amount of energy per gram during respiration?

    • Lipids
    • Proteins
    • Carbohydrates
    • Nucleic acids

  14. A mouse changes from a high-carbohydrate diet to a high-fat diet. What change in RQ is expected?

    • RQ rises towards 1.5
    • RQ rises to 2.0
    • RQ falls towards 0.7
    • RQ stays exactly 1.0

  15. What does a respiratory quotient (RQ) value of 0.85 indicate about the substrates being respired?

    • Pure lipid
    • Mixed substrates
    • Pure carbohydrate
    • Pure protein

  16. What is the respiratory quotient of tissue consuming 40 cm3 oxygen and producing 36 cm3 carbon dioxide?

    • 0.90
    • 1.00
    • 1.11
    • 0.80

  17. An organism respires 10 g of lipid and, separately, 10 g of carbohydrate. Approximately how much more energy is released by the lipid?

    • About 23 kJ more
    • About 230 kJ more
    • About 160 kJ more
    • About 2300 kJ more

  18. What is the expected respiratory quotient (RQ) value when lipids are used as the sole respiratory substrate?

    • 0.9
    • 0.5
    • 1.0
    • 0.7

  19. Why does lipid oxidation require more oxygen per carbon dioxide molecule produced than carbohydrate oxidation?

    • Fewer hydrogen atoms
    • More carboxyl groups
    • Lower oxygen content
    • Higher oxygen content

  20. What is the RQ when 50 mm3 of oxygen is consumed and 40 mm3 of carbon dioxide is produced?

    • 1.25
    • 1.0
    • 0.7
    • 0.8

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