Creation of a proton gradient by the electron transport chain represents

Potential Energy

Explanation:

The electron transport chain is a series of proteins and organic molecules located in the inner membrane of the mitochondria. During electron transfer and proton pumping electrons are moved from a higher energy level to a lower one and in the process release energy. This energy is used to make ATP. It is stored in the electrochemical gradient of protons and it has to be released for electron transport to continue.