Explain. Large amounts of potential energy are released when oxygen is the electron donor, because oxygen is so electronegative. The large amount of energy is required for large body size and high growth rates. Large amounts of potential energy are released when oxygen is the electron donor, because oxygen is so electropositive. The large amount of energy is required for large body size and high growth rates. Oxygen allows UV light to get to the organisms, which is required for efficient cellular respiration, large body size and high growth rates. Large amounts of potential energy are released when oxygen is the electron acceptor, because oxygen is so electronegative. The large amount of energy is required for large body size and high growth rates.