Virtuelle (Nano) Welten: PDB Molecule of the Month 22: Photosystem I

Harvesting Light

Of course, plants do not rely on the slim chance of a photon running into one tiny chlorophyll molecule in the middle of the reaction center. As with all things in life, cells have found an even better way. Photosystem I, shown here looking from the top, contains an electron transfer chain, colored here in bright colors, at the center of each of the three subunits. Each one is surrounded by a dense ring of chlorophyll and carotenoid molecules that act as antennas. In this picture, the protein is transparent so that only the cofactors are seen. These antenna molecules each absorb light and transfer energy to their neighbors. Rapidly, all of the energy funnels into the three reaction centers, where is captured to create activated electrons.