During aerobic respiration, cells respire substrates such as glucose to produce ATP. Some events that occur during aerobic respiration are: • The respiratory substrate breaks down into smaller and smaller molecules. These series of reactions are described as catabolism. • Coenzymes take part in various reactions. In some reactions, coenzymes are reduced or oxidised. • Carbon dioxide is released.

1. (a)Aerobic respiration occurs in four successive stages: glycolysis (G), link reaction (LR), Krebs cycle (KC) and oxidative phosphorylation (OP). Complete Table 3.1 to show which events occur in each stage of aerobic respiration. Use a tick (✔) to show that the event does occur or a cross (X) to show that the event does not occur.[4]
2. (b)(i)A new hand-held technological device shows the main type of respiratory substrate being used in the cells of a person. The device consists of a carbon dioxide sensor and air-flow meter. The person inhales through the device for a fixed time and then exhales into it. The device calculates the respiratory quotient (RQ) value to show whether the cells are mainly respiring carbohydrates or lipids. Explain how the device calculates the RQ value and how this shows whether the cells are mainly respiring carbohydrates or lipids.[4]
3. (b)(ii)State the difference in the relative energy values of carbohydrates and lipids as respiratory substrates, and explain the reasons for the difference.[3]