Structure & Function of Light Dependent Reactions
Author: Dragana Zekanovic
The light dependent reactions occur in the thylakoid membranes of the chloroplast. Photosytem I and Photosytem II are the strucutures of the reactions. Photosystem II comes before photosystem I. P680 a special pair of photosystem II absorbs energy, it then enters an excited (high-energy) state. It absorbs a wavelength of 680 nm and the reaction center chlorophyll a of phtosystem II called p680. Electrons are then passed onto the electron transport chain in a series of redox. As the electron leaves PSII it is in . transfered from an organic molecule to a protein. The electron goes from higher to lower energy in Photosystem I. Some of this energy is then used to pump H+ ions from the stroma into the thylakoid. PSI is most efficient at absorbing a wavelength of 700 nm and the reaction center chlorophyll a of phtosystem II called p700 . The linear electron flow includes the electrons through each photosystems to produce ATP and light energy (ATP). The reactions incude three major processes. First, excited electrons leave chlorophyll and reduce NADP+ into NADPH (photosystem 1). Second, electrons which move through the electron transport chain provide free energy necessary to pump hydorgen ions into the inner thylakoid (photosystem 2). Last, ADP is converted into ATP by the hydrogen ions flowing out of the tylakoid by a protein channel (ATP synthase).
(https://www.khanacademy.org/science/biology/photosynthesis-in-plants/the-light-dependent-reactions-of-photosynthesis/a/light-dependent-reactions)