Outline7 marksChallenge
A student uses a simple respirometer to determine the respiratory quotient (RQ) of germinating mung bean seeds at 25 °C. The student first measures oxygen consumption using soda lime to absorb carbon dioxide, and then measures carbon dioxide production without soda lime. The following table shows RQ values for different pure respiratory substrates when fully oxidised.
| Substrate | RQ |
|---|---|
| Glucose | 1.0 |
| Lipid (tripalmitin) | 0.70 |
| Protein (casein) | 0.90 |
Outline how the respirometer is used to measure oxygen consumption and carbon dioxide production, and how the RQ is calculated. Use the data to explain how RQ can identify the main respiratory substrate being used. Outline two features of ATP that make it a suitable universal energy currency and state two reasons why energy is required by living organisms.