Different types of respiratory substrate can have different energy values and therefore release different quantities of energy when they are respired. Complete Table 1.1 to show the energy value of each of the three main types of respiratory substrate. Use one tick (✔) to identify which of the two possible energy values is correct for each respiratory substrate. Table 1.1 type of respiratory substrate carbohydrate lipid protein energy value/kJg-1 approximately 17 approximately 37 (b) Determining the respiratory quotient (RQ) of an organism can be used to indicate the main type of respiratory substrate that is being metabolised in respiration. This is because the different types of respiratory substrate have different RQ values. Table 1.2 shows typical RQ values for carbohydrate, lipid and protein. Table 1.2 type of respiratory substrate RQ value carbohydrate 1.0 lipid 0.7 protein 0.8 (c) Organic acids such as malic acid can also act as respiratory substrates. When respired aerobically, their RQ values may be different to the RQ values of the main respiratory substrates. Fig. 1.1 shows the formula that is used to calculate RQ values. RQ = number of molecules of carbon dioxide produced number of molecules of oxygen taken in Fig. 1.1 When malic acid is respired aerobically, the equation is: C4H6O5 + O2 4CO2 + 3H2O + energy (d) The deer mouse, Peromyscus maniculatus, lives in forests in North America. [Figure 1.2] The deer mouse is active throughout the year and is much more active during the night than during the day. At certain times of the year, deer mice spend a number of hours during the day in a physiologically controlled state of inactivity (not active), known as torpor. During this time there is a decrease in metabolic rate. Fig. 1.3 is a graph showing the RQ of a deer mouse from 6:00 to 22:00 on a day that included time in torpor. [Figure 1.3]