(a) The results of investigations carried out on mitochondria show how the structure of a mitochondrion is related to its role in aerobic respiration. • Intact mitochondria (not damaged) were removed from cells. • A technique was used to remove the outer mitochondrial membrane, leaving the inner membrane intact. • The inner mitochondrial membrane was separated from the contents of the matrix so that both could be analysed.

1. (a)(i)The removal of the outer membranes of mitochondria involves placing the organelles in pure water. This results in the rupture (bursting) of the outer membrane. The inner mitochondrial membrane does not rupture and remains intact. Suggest and explain why the inner membrane of a mitochondrion remains intact when the organelle is placed in pure water.[2]
2. (a)(ii)Name three molecules, other than coenzymes, that are found in the mitochondrial matrix and explain their role in aerobic respiration.[3]
3. (a)(iii)The inner membrane contains a very high proportion of the molecule cardiolipin. Cardiolipin makes the membrane impermeable to some ions. Suggest why the inner membrane contains a very high proportion of cardiolipin.[1]
4. (b)In further experiments it was found that, in an intact mitochondrion: • there is a membrane potential across the inner mitochondrial membrane, with the matrix having a negative charge • the transport of ATP, ADP and inorganic phosphate (Pᵢ) is driven by the membrane potential across the inner membrane. Fig. 3.1 shows the location of some inner membrane carrier proteins. [Figure 3.1]
5. (b)(i)Reduced NAD and reduced FAD transfer hydrogen atoms to carriers located in the inner mitochondrial membrane. Explain how hydrogen atoms from reduced NAD and reduced FAD lead to a membrane potential forming across the inner mitochondrial membrane during oxidative phosphorylation.[4]
6. (b)(ii)Suggest and explain how Pᵢ is transported across the inner membrane of the mitochondrion into the matrix.[2]
7. (b)(iii)Suggest the advantages of linking ATP transport to ADP transport across the inner membrane of the mitochondrion.[2]

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