Ferredoxin (Fd) is found in chloroplasts which mediates electron transfer and contains an iron-sulfur cluster. It is involved in the photosynthesis process where its iron atoms accept or discharge electrons when they are being oxidized or reduced. The iron-sulfur cluster can contain 2Fe-2S and is termed plant-like or 3Fe-4S or 4Fe-4S clusters. Adrenodoxin (ADR) is a ferredoxin containing a 2Fe-2S group involved in electron transfer from NADPH+ to a cytochrome P-450 in the adrenal gland. Putidaredoxin (PUT) and terpredoxin (TER) are involved in the same reaction in bacteria and contain a 2Fe-2S group.