Electron transfer chain of photosystem I. The heart of photosystem I is an electron transfer chain, a chain of chlorophyll (shown in green), phylloquinone (shown in orange) and three iron-sulfur clusters (yellow and red at the top). These cofactors convert the energy from light into energy that the cell can use. October 2001, David Goodsell | doi:10.2210/rcsb_pdb/mom_2001_10 | RCSB PDB, CC-BY-4.0 Zygote Quarterly 28 | vol 2 | 2020 | ISSN 1927-8314 | Pg 135 of 140