24 8 The electron transport chain generates ATP. The diagram shows the electron transport chain. carrier (oxidised) carrier (reduced) carrier (oxidised) reduced NAD water carrier (reduced) carrier (oxidised) carrier (reduced) oxidised NAD oxygen ATP ATP ATP (a) State the location of the electron transport chain in a mitochondrion. (1) .................................................................................................................................................................................................................................................................................... (b) Hydrogen cyanide gas is a poison that can kill an animal if it is inhaled. Cyanide is a non-competitive inhibitor of the enzyme cytochrome oxidase. Cytochrome oxidase is the last carrier in the electron transport chain. (i) Explain why hydrogen cyanide gas can kill an animal. (5) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 25 Turn over (ii) A dose of 1.0 mg of hydrogen cyanide per kilogram of body mass is fatal. An animal with a body mass of 10 kg inhaled air containing 0.24 mg dm−3 of hydrogen cyanide. The animal breathed at a rate of 15 dm3 of air per minute. Calculate how many minutes it would take for this animal to obtain a fatal dose. Give your answer to three significant figures. (3) Answer .............................................................. minutes (c) The effect of cyanide on oxygen uptake by mitochondria was investigated using the following method: ● suspend mitochondria in a flask containing a buffer solution ● measure the concentration of oxygen in the flask for the first five minutes ● then add a respiratory substrate and ADP to the flask ● measure the concentration of oxygen in the flask for the next 10 minutes ● then add cyanide solution to the flask ● measure the concentration of oxygen in the flask for the next 10 minutes. The graph shows the results for the first five minutes. Complete the graph to show the results for the next 20 minutes. (2) 25 20 15 10 5 0 Time / minutes Oxygen concentration (Total for Question 8 = 11 marks)