Ferredoxin is a small iron-sulfur protein found in various organisms, including bacteria, plants, and animals. It plays a crucial role in electron transfer processes, facilitating the movement of electrons in biochemical reactions, particularly in photosynthesis and cellular respiration. In plants, ferredoxin is essential for the conversion of light energy into chemical energy during photosynthesis. It acts as an electron carrier, transferring electrons from photosystem I to other proteins involved in the production of NADPH and ATP, which are vital for the plant's energy needs.