Oxidative phosphorylationEdexcel A-Level Biology B: Mind map

Exam questions on Oxidative phosphorylation

1. Isolated mitochondria are suspended in a buffered medium containing a pH electrode. The outer membranes of the mitochondria are permeable to small ions. When NADH and oxygen are added, the pH of the medium falls, and ATP is formed if ADP and phosphate are also present.
   Explain why the pH of the medium falls after NADH and oxygen are added.2 marks
2. A researcher adds a chemical to isolated mitochondria that makes the inner membrane freely permeable to protons. Electrons continue to pass along the electron transport chain, and oxygen continues to be used at a high rate, but ATP production almost stops.
   Explain why ATP production almost stops.2 marks
3. Cyanide binds to the last protein carrier in the electron transport chain and prevents it from passing electrons to oxygen. Cells exposed to cyanide soon run short of ATP, even though plenty of glucose is available. The Krebs cycle in these cells also stops.
   Explain why cells exposed to cyanide soon run short of ATP.3 marks