The Electron Transport Chain (ETC) is an example of an exergonic reaction.
Here’s why: The ETC is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions. This process releases energy, which is used to create a proton gradient across the inner mitochondrial membrane. The energy stored in this gradient is then used to produce ATP, the energy currency of the cell.
An exergonic reaction is one that releases energy, and since the ETC releases energy as electrons move through the chain, it fits this definition. In contrast, an endergonic reaction requires energy input to proceed, which is not the case for the ETC.
In summary, the Electron Transport Chain is an exergonic process because it releases energy that is harnessed to produce ATP.