CAIE A Level Biology 9700 · Energy and respiration
A student places germinating barley seeds in a simple respirometer and measures the gas volumes over a 12-hour period. The results are shown in the table.
| Gas | Volume (cm³) |
|---|---|
| Oxygen consumed | 10.0 |
| Carbon dioxide produced | 7.0 |
Describe how the student can use these data to determine the respiratory quotient (RQ) and explain what the RQ value indicates about the respiratory substrate used by the seeds.
3 marks, so the mark scheme is looking for about 3 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.