Question

imagine a cell is treated with a mystery chemical that inactivates the first enzyme in the citric acid cycle. which two events in cellular respiration would be directly inhibited by this mystery chemical? select the two best answers. electron flow through the electron transport chain reduction of fad atp synthase activity reduction of nad+ complex ii activity what would most likely happen to a cells ability to generate atp if it was treated with this mystery chemical? atp generation would increase because there would be more nadh and fadh2 to power the electron transport chain. atp generation would increase because the enzymes in glycolysis would function more efficiently. atp generation would decrease because there would be less nadh and fadh2 to power the electron transport chain. atp generation would decrease because the enzymes in glycolysis could no longer function.

Explanation:

• In the citric acid cycle, reduction of \(FAD\) (to \(FADH_2\)) and reduction of \(NAD^{+}\) (to \(NADH\)) occur during the cycle reactions. If the first enzyme is inactivated, the cycle cannot proceed, so these reduction reactions (which are part of the cycle's normal operation) are directly inhibited.
• For ATP generation: The citric acid cycle produces \(NADH\) and \(FADH_2\) which are used in the electron - transport chain to make a large amount of ATP via oxidative phosphorylation. If the citric acid cycle is inhibited (by inactivating the first enzyme), less \(NADH\) and \(FADH_2\) are produced. With less \(NADH\) and \(FADH_2\), the electron - transport chain (which relies on these electron carriers) will produce less ATP. Glycolysis is not directly affected by the inactivation of the first citric acid cycle enzyme, so the decrease in ATP is due to less \(NADH\) and \(FADH_2\) for the electron - transport chain.

Answer:

• First part (two events): reduction of \(FAD\), reduction of \(NAD^{+}\)
• Second part (ATP generation): ATP generation would decrease because there would be less \(NADH\) and \(FADH_2\) to power the electron transport chain.