Question

Inhibitors of the electron transport chain exert their effects through a variety of mechanisms.

Answer 1

Answer:

Azide and Carbon monoxide block electron transport and proton pumping via inhibition of Complex IV.

Rotenone blocks electron transport and proton pumping via inhibition of Complex I.

Atractyloside blocks electron transport and ATP synthesis by inhibiting the exchange of ATP and ADP across the inner mitochondrial membrane.

Explanation:

The mitochondrial electron transport chain is composed of different complexes integrated into the inner mitochondrial membrane, which function to generate an electrochemical proton (H+ ions) gradient that is then used to drive the synthesis of ATP, the energy coin of the cell. The mitochondrial complex I catalyzes the electron transfer from nicotinamide adenine dinucleotide (NADH) to ubiquinone and then transports H+ ions across the inner mitochondrial membrane. Moreover, the mitochondrial complex IV, also known as Cytochrome c oxidase, receives electrons via the cytochrome pathway in order to complete the reduction of oxygen (O2) into two molecules of water (H2O). Azide is a selective inhibitor of the complex IV which acts as an uncompetitive inhibitor with regards to O2, while carbon monoxide (CO) binds to the cytochrome c oxidase enzyme, thereby suppressing its activity and thus disturbing ATP synthesis. Rotenone is a potent inhibitor of the mitochondrial complex I that inhibits electron transfer from the iron-sulfur centers in the complex I to ubiquinone, thereby blocking ATP synthesis. Finally, atractyloside is a competitive inhibitor that inhibits the transport of ADP across the mitochondrial inner membrane by blocking the ADP/ATP translocator, thereby preventing ADP from entering mitochondria.