Question

which is a correct example of energy coupling using ATP? Please choose the correct answer

A. The electron transport chain uses ATP to pump protons against their electrochemical gradient.

B. Hydrolyzing ATP to drive an anabolic reaction.

C. Substrate level phosphorylation makes ATP.

D. In photosynthesis, light energy is trapped into an ATP molecule.

Answer 1

The correct option is :

Answer: B

Hydrolysing ATP to drive an anabolic reaction.

Explaination:

ATP is an energy rich compound called energy currency of the cell. ATP hydrolysis is highly exergonic reaction. In energy coupling the energy released by the hydrolysis of ATP is supplied to metabolic reactions which are endergonic. Anabolic reactions are endergonic and hence require energy to occur. Thus, during anabolic reactions hydrolysis of ATP is coupled to the reactions which are endergonic, i.e. anabolic reactions.

Other options are incorrect because:

A. The electron transport chain does not use ATP to pump protons against concentration gradient.

In electron transport chain the energy released from the oxidation-reduction reactions is used to pump protons from the mitochondrial matrix into the intermembrane space. when the electrons move from NADH and FADH₂ to final electron acceptor, oxygen through the complexes of the electron transport chain energy is released and this energy pumps protons against concentration gradient.

C. Substrate level phosphorylation makes ATP, but in energy coupling using ATP, ATP are hydrolyzed. Thus, this option is incorrect.

D. Again during photosynthesis light energy is trapped which is stored in ATP, i.e. ATP is synthesized not hydrolysed. Thus it is not energy coupling using ATP.