Tiêu đề Feb-March_2025_9700_42_QP - Crack A Level.pdf ✅

2 © UCLES 2025 9700/42/F/M/25 1 (a) 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 (3) to identify which of the two possible energy values is correct for each respiratory substrate. Table 1.1 type of respiratory substrate energy value/kJg –1 approximately 17 approximately 37 carbohydrate lipid protein [1] (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 (i) State the name of the laboratory apparatus that can be used to determine the RQ value of organisms such as blowfly larvae. ..................................................................................................................................... [1] (ii) When determining RQ values using the laboratory apparatus stated in (b)(i), chemicals such as soda lime or potassium hydroxide solution are used. State the reason for using chemicals such as soda lime or potassium hydroxide solution when measuring RQ values. ..................................................................................................................................... [1] * 0000800000002 * , , ĬÝú®Ġ ́íÈõÏĪÅĊàû ̧þ× ĬÀīñØīĉÿÕùāþÌí°êĖĂ ĥμåĕμĕĥÕĕĥĥąąĕąĕõÕ DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN
3 © UCLES 2025 9700/42/F/M/25 [Turn over (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 (i) Calculate how many molecules of oxygen are taken in when one molecule of malic acid is respired aerobically. number of molecules of oxygen = ......................................................... [1] (ii) Calculate the RQ for malic acid. Give your answer to two decimal places. RQ = ......................................................... [1] * 0000800000003 * , , Ĭßú®Ġ ́íÈõÏĪÅĊàù ̧þ× ĬÀĬòÐĝąïäÿðËĐąĬêĦĂ ĥμÕÕõõąμąĕμąąõĥÕĥÕ DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN