A scientist was studying the electron transport chain and developed a compound that bound to all the cytochromes in the proteins of the electron transport chain. Once bound, the compound blocked electron acceptance by the iron in the heme group of the cytochrome. Which one of the following would be most likely to occur in the presence of an oxidizable substrate?
Agents that act on components of the electron transport chaina. If there is a block at any point in the electron transport chain, all carriers before the block will accumulate in their reduced states, whereas those after the block will accumulate in their oxidized states. As a result, O2 will not be consumed; ATP will not be generated; and the TCA cycle will slow down because of the accumulation of NADH.(1). Rotenone, a fish poison, complexes with complex I, causing NADH to accumulate. It does not block the transfer of electrons to the chain from FADH2 .(2). Antimycin (antibiotics) block the passage of electrons through the cytochrome b-c1 complex (complex III).(3). Cyanide and carbon monoxide, poisons commonly used for suicide, combine with cytochrome oxidase (complex IV) and block the transfer of electrons to O2 .If the cytochromes are inhibited, ATP production, the electrochemical potential, heat production from NADH oxidation, and succinate oxidation all decrease because electron flow is not permitted. The rapid drop in ATP levels will lead to cell death.
The amount of heat generated from NADH oxidation would increase.
The rate of succinate oxidation would not be affected.
ATP could still be generated from the oxidation of NADH by transfer of electrons to O2.
Cell death would result from a lack of ATP.
Respiratory Chain