Oxidative phosphorylationEdexcel A-Level Biology A: Flashcards

Exam questions on Oxidative phosphorylation

1. A student is revising the final stage of aerobic respiration. This stage takes place on the inner membrane of the mitochondrion, where reduced NAD and reduced FAD from the earlier stages deliver hydrogen to a series of electron carriers called the electron transport chain.
   Explain why the Krebs cycle stops when no oxygen is available, even though oxygen is not used in the cycle.2 marks
2. A researcher suspends intact mitochondria in a solution containing oxygen, ADP and phosphate, and monitors the pH in the space between the inner and outer mitochondrial membranes. When reduced NAD is added, the pH of this space falls and ATP is made. When cyanide is then added, the pH rises again and ATP production stops.
   Describe how ATP is made when protons move through ATP synthase.2 marks
3. The inner membrane of a mitochondrion is folded into cristae. It is almost impermeable to protons (hydrogen ions) and contains electron carriers arranged in sequence, together with many molecules of the enzyme ATP synthase. The outer membrane is permeable to small molecules.
   Explain how the electron transport chain creates a proton gradient across the inner mitochondrial membrane.3 marks