1. Experiments in respiration, RQ and alternative substrates

2. Respiratory rate The respiratory rate is the rate at which an organism converts glucose to CO 2 and water. It can be calculated by measuring an organism’s rate of oxygen consumption. Studies on simple animals often use a respirometer. Respirometers measure the change in gas volume in a closed system. Any change is due to the respiratory activity of the study organisms. Potassium hydroxide or soda lime is used to absorb the carbon dioxide produced, meaning any changes in volume are due to oxygen consumption.

3. The respirometer

4. Respirometer experiments

5. Respiratory substrates The difference in the relative energy values of these respiratory substrates is due to the amount of hydrogen atoms present in each one. If more hydrogen atoms are available to reduce coenzymes, more energy can subsequently be generated in the electron transport chain. Other substances as well as glucose can be respired. Different respiratory substrates release different amounts of energy. Respiratory substrateMean energy value (kJ g -1 ) carbohydrate lipid protein 15.8 39.4 17.0

6. Respiration calculations