ANSWER:
they dont make their own food only photosynthetic creatures can.
~batmans wife
The substrate of the citric acid cycle which can block respiration when it is present in excess is MALONATE. Malonate inhibits respiration by competing with succinate dehydrogenase for its acitve site. Malonate binds to the active site without reacting, thus competing with succinate. This disrupts the cellular respiration in the cell.