Duroquinol was discovered to act as an electron donor in chloroplasts, helping with electron transfer reactions. It can transfer electrons to oxygen quickly, leading to ATP production. Spectroscopic studies showed that key electron carriers in chloroplasts were reduced by duroquinol in the dark. The process involves a sequence of electron carriers including plastoquinone, the "Rieske" iron-sulfur center, cytochrome f, plastocyanin, and P-700.