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CAIE A-Level Biology A2 12.1.5 Respiratory Quotient Rq Questions

Write carbon dioxide produced over oxygen taken in before interpreting the value. An RQ near 1.0 indicates carbohydrate, about 0.7 indicates lipid, and changing or higher values require metabolic context.

Syllabus
2028–2030
Course
Biology 9700
Level
A2

Exam points

  • Define respiratory quotient as the amount or volume of carbon dioxide produced divided by the amount or volume of oxygen taken in during respiration.
  • Use RQ values near 1.0, 0.7 or between them to identify carbohydrate, lipid or mixed-substrate respiration and explain changes as substrates are depleted.
  • Interpret an RQ above 1.0 during intense exercise as evidence of anaerobic respiration, reduced oxygen availability or increased carbon-dioxide release.

CAIE A-Level Biology A2 12.1.5 Respiratory Quotient Rq Questions question 1

[Maximum number: 4]

Question (a)

(a)

The rufous hummingbird, Selasphorus rufus, feeds on the nectar produced by flowers. Nectar is a liquid containing sugars. Hummingbirds hover to maintain a position next to a flower while they feed. This requires a lot of energy.

Fig. 6.2 is a rufous hummingbird.

Fig. 6.2

Fig. 6.2

Hummingbirds that have not fed for some time have a respiratory quotient (RQ) value of 0.7 . After feeding their RQ value is 1.0 .

[ 4 ]

Question (i)

(i)

Define the term respiratory quotient.

[ 2 ]

Question (ii)

(ii)

Explain why a hummingbird that has not fed for some time has an RQ value of 0.7 , while a hummingbird that has fed has an RQ value of 1.0.

[ 2 ]
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