Malonate inhibits a reaction in the Krebs cycle - AQA - A-Level Biology - Question 2 - 2021 - Paper 1

Malonate acts as a competitive inhibitor for succinate dehydrogenase, an enzyme in the Krebs cycle. When malonate is present, it competes with succinate for binding to the active site of succinate dehydrogenase. This inhibits the conversion of succinate to fumarate, ultimately slowing down the Krebs cycle. Since the Krebs cycle is linked to the electron transport chain, a reduced rate of the cycle means fewer electrons are available to be passed along this chain, leading to a decrease in the production of ATP and the consumption of oxygen, as oxygen is used as the final electron acceptor in cellular respiration.