Endergonic Reactions are characterized by which of the following?

• A. They occur without energy
• B. They are spontaneous
• C. They require input of energy to occur
• D. They release energy as they proceed

Answer: (C)

Endergonic reactions require input of energy to occur because they increase the system’s free energy. In these reactions, the products have more free energy than the reactants (ΔG is positive), so an energy source must drive the process. That’s why they aren’t spontaneous under standard conditions and often rely on coupling to energy-yielding steps (like ATP hydrolysis) to proceed.

If a reaction released energy or could happen without energy input, it would be exergonic with a negative ΔG, not endergonic.