Question

Poisons like cyanide inhibit $N{a}^{+}$ efflux and $K^{+}$ influx. The effect is reversed by injection of ATP. It shows that

• A. $N{a}^{+}-K^{+}$ pump operates fully in cells
• B. ATP is hydrolysed by ATPase to release
  energy
• C. Energy for $N{a}^{+}-K^{+}$ pump comes from ATP hydrolysis
• D. ATP is a carrier protein

Answer 1

Answer: (C)

There are many enzyme inhibitors in our body that inhibit enzyme function in many ways, these inhibitors are of the following types.
Competitive inhibitor: In these, the inhibitor does competition with the substrate and decreases product formation. Ex- malonate is an inhibitor of succinate substrate on succinate dehydrogenase enzyme and cyanide is an inhibitor of cytochrome c oxidase.
Non-competitive inhibitor: In these, inhibitors does not compete with the substrate but changes the attachment sites for the substrate on enzyme due to which the product formation becomes zero.
Cyanide binds with the fourth complex that is "cytochrome c oxidase" of the electron transport chain and inhibits its usual action. Cyanide binds to the iron present in the protein complex and inhibits the transport of electrons to oxygen and stop ATP production. Cyanide stops the Na+ and K+ efflux during cellular transport since the protons are not allowed to return into the mitochondrial matrix. When ATP is injected which provides consequent energy to the Na+/-K+ exchange pump, this inhibitory effect is reversed. This demonstrates that the Na+/-K+ exchange pump gets energy from ATP.