How does ATP participate in energy-coupling reactions?
a) Hydrolysis of ATP fuels endergonic reactions.
b) Hydrolysis of ADP fuels endergonic reactions.
c) Synthesis of ATP fuels exergonic reactions.
d) Synthesis of ADP fuels exergonic reactions.

• A. Hydrolysis of ATP fuels endergonic reactions.
• B. Hydrolysis of ADP fuels endergonic reactions.
• C. Synthesis of ATP fuels exergonic reactions.
• D. Synthesis of ADP fuels exergonic reactions.

Answer: (A)

Verified step by step guidance

1. Understand the concept of energy-coupling: Energy-coupling in cells involves using energy released from exergonic reactions to drive endergonic reactions. ATP (adenosine triphosphate) is a key molecule in this process.
2. Recognize the role of ATP hydrolysis: ATP hydrolysis is an exergonic reaction where ATP is broken down into ADP (adenosine diphosphate) and an inorganic phosphate, releasing energy.
3. Identify how ATP hydrolysis fuels endergonic reactions: The energy released from ATP hydrolysis is used to drive endergonic reactions, which require an input of energy to proceed.
4. Differentiate between ATP and ADP in energy coupling: While ATP hydrolysis releases energy, the synthesis of ATP from ADP and inorganic phosphate is an endergonic process that requires energy input, often from exergonic reactions.
5. Connect the concepts: In cellular metabolism, ATP acts as an energy currency, where its hydrolysis provides the energy needed for various cellular processes, effectively coupling exergonic and endergonic reactions.