During this process, ATP is generated by the Photosystem II electron transport chain and chemiosmosis. These photosystems include units called antenna complexes composed of chlorophyll molecules and accessory pigments located in the thylakoid membrane. This splits the water molecule, generating oxygen and hydrogen ions. Photosystem II (PSII) is a specialized protein complex that uses light energy to drive the transfer of electrons from water to plastoquinone, resulting in the production of oxygen and the release of reduced plastoquinone into the photosynthetic membrane. Photobiological H2 production is an attractive option for renewable solar fuels. There are two types of photosystems found in most plants: photosystem I (PSI) and photosystem II (PSII). It produces atmospheric oxygen to catalyze the photo-oxidation of water by using light energy. As the accumulating protons in the thylakoid interior space pass back across the thylakoid membrane to the stroma through ATP synthetase complexes, this proton motive force is used to generate ATP from ADP and Pi. So it is called P700. The combined action of the entire photosynthetic electron transport chain also produces a proton-motive force that is used to generate ATP. It is also seen in certain photosynthetic bacteria. It captures photons and uses the energy to extract electrons from water molecules. Photosystem II (PSII) uses visible light to oxidize water and release O 2. 4.Photosystem I is sensitive to light wavelengths of 700 nm while photosystem II is sensitive to light wavelengths of 680 nm. Photosystem II (PSII) uses light energy to split water into chemical products that power the planet. The electrons transported down the Photosystem I electron transport chain combine with 2H+ from the surrounding medium and NADP+ to produce NADPH + H+. Photosystem II is named as such because it was discovered after photosystem I. Photons are absorbed by chlorophyll and accessory pigments and that energy is eventually transfered to the reaction center where it is absorbed by an excitable electron moving it to a higher energy level. 2.Photosystem II produces ATP while photosystem I produces NADPH. Photosystem II is the first membrane protein complex in oxygenic photosynthetic organisms in nature. Main Difference – Photosystem 1 vs 2. Hydrogen is an essential commodity with over 60 million tons produced globally every year. Once in the reaction centre, the energised electron is transferred to a specialised pair of chlorophyll molecules called P680. 2. Photoexcited electrons travel through the cytochrome b6f complex to photosystem I via an electron transport chain set in the thylakoid membrane. Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS). Still have questions? Both carry out the light reaction of photosynthesis. Figure \(\PageIndex{3}\): Electron Transport and Chemiosmosis during Photosynthesis 1. Photosystem II contains chlorophyll a molecules referred to as P680 because they have an absorption peak of 680 nanometers. We will now look at Photosystems I and II and their roles in noncyclic photophosphorylation. The deficit is due to photo-excitation of electrons which are again trapped in an electron acceptor molecule, this time that of photosystem I. Photosystems are z shaped. Two kinetically distinguishable phases in the formation of the spin trap-hydroxyl (POBN-OH) adduct EPR signal were observed: the first phase (t1/2 = 7.5 min) and the second phase (t1/2 = 30 min). Photosystem II, the Evolution of Non-cyclic Photosynthesis Photosynthesis first evolved as an anoxygenic process in bacteria that were similar to the current green sulphur bacteria, where the transmission of an electron from the photosystem is accompanied by the extraction of a proton from hydrogen sulphide (H 2 S), producing sulphur as a by-product. However, during the process of photosynthesis, photosystem II comes into play before photosystem I. However over 95 percent of it is made by steam reformation of fossil fuels, a process that is energy intensive and produces carbon dioxide. There are two main photosystems; photosystem I (PS I) and photosystem II (PS II), present in the thylakoid membranes of chloroplasts in plants. Photosystem II is the first step of photosynthesis, where the chlorophyll molecule uses light energy to take an electron from a water molecule. 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