Photosystem II (PSII) is a membrane protein complex which functions to catalyze light-induced water oxidation in oxygenic photosynthesis. Electrons first travel through photosystem II and then photosystem I. While at photosystem II and I, the electrons gather energy from sunlight. The light-dependent reactions begin in a grouping of pigment molecules and proteins called a photosystem. In photosystem II, the electron comes from the splitting of water, which releases oxygen as a waste product. In photosystem I, the electron comes from the chloroplast electron transport chain. Photosystem I have chlorophyll a molecule which takes in optimum light of 700 nm and is called P700, whereas the reaction center of photosystem II has P680, the form of chlorophyll a which takes in best the light of 680 nm. A photon of light energy travels until it reaches a molecule of chlorophyll. Chlorophyll can be found in _____. C. 6. This process is similar to the electron transport chain in the mitochondria of cells. A Photosystem II splits water into 1/2 O2, H+, and e- . 5. Photosystems exist in the membranes of thylakoids. Each photosystem is made of two components: 1) antenna complex that consists of 300-400 chlorophyll a and b molecules and other accessory pigments such as carotenoids and 2) reaction center that consists of one or more chlorophyll molecules with a primary electron acceptor. Photosystem I The light absorption processes associated with photosynthesis take place in large protein complexes known as photosystems. 5. 6 O 2 + 12 NADPH + 18 ATP. Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+. The Electron Transport Chain. There are 2 photosystems, photosystem I (PS I) and photosystem II (PS II). Later, photosystem II was discovered and found to be earlier in the electron transport chain. PS2 powers the pumping of H ions into the lumen of the cell. Treatment of lamellar fragments with neutral detergents releases these particles, designated photosystem I and photosystem II, respectively. Photosystem I can be excited by light of wavelengths shorter than 700 nm, but photosystem II requires light of wavelengths shorter than 680 nm for excitation. The light-dependent reactions involve two photosystems called Photosystem I and Photosystem II.These photosystems include units called antenna complexes composed of chlorophyll molecules and accessory pigments located in the thylakoid membrane.Photosystem I contain chlorophyll a molecules called P700 because they have an … In the electromagnetic spectrum, the type of radiation that we call visible light occurs between _____. 3. Describe an antenna complex and state the function of the reaction center. Both photosystems must operate for the chloroplast to produce NADPH, ATP, and O 2 , because the two photosystems are connected by the electron transport chain. Abstract. A & C. 7. Photosystem II reaction centers (RC) consist of D1 and D2 polypeptides and a bound cytochrome b 559. Briefly describe the overall function of Photosystem II in the light-dependent reactions of photosynthesis. Photosystem I was discovered first. Photosynthesis - Photosynthesis - Photosystems I and II: The structural and photochemical properties of the minimum particles capable of performing light reactions I and II have received much study. The process of photosynthesis begins with energy from light being absorbed by photosystem II (PS2). 2. The one known as Photosystem I contains a chlorophyll dimer with an absorption peak at 700 nm known as P700.. Photosystem I makes use of an antenna complex to collect light energy for the second stage of non-cyclic electron transport. These are called so in order of their discovery. But it was too late, the name stuck. 4. Flow of Energy from Photosystem 2. A pigment molecule in the photosystem absorbs one photon, a quantity or “packet” of light energy, at a time. State the reactants and the products for the light-dependent reactions. Isolated RC, named D1/D2 particles, contain 4–6 Chl a, 1 β-carotene and 1 or 2 cytochrome b 559 per two pheophytin a molecules (1).Polypeptides D1 and D2 exhibit marked homologies with the L and M subunits of the RC of purple bacteria, respectively (2).