Question

Poisons like cyanide inhibit Na⁺ efflux and K⁺ I influx during cellular transport. This inhibitory effect is reversed by an injection of ATP. This demonstrates that

• A. ATP is the carrier protein in the transport system
• B. energy for Na⁺-K⁺ exchange pump comes from ATP
• C. ATP is hydrolysed by ATPase to release energy
• D. Na⁺-K⁺ exchange pump operates in the cell.

Answer 1

Answer: (B)

Active transport is uphill movement of materials across the membrane where the solute particles move against their chemical concentration or electrochemical gradient. Hence the transport requires energy in the form of ATP. Metabolic inhibitors like cyanide inhibit absorption of solutes by lowering the rate of respiration. Consequently less ATP are formed. However, by adding ATP, active transport is facilitated. It occurs in plants as in climacteric fruits and under cold stress. ATP synthesis does not occur. Reducing power present in reduced coenzymes is oxidised to produce heat energy. Therefore, the heat liberation pathway of terminal oxidation is cyanide resistant. In normal aerobic respiration, the effect of cyanide poisoning can be minimised by immediate supply of ATP.