D) oxygen Movement of H+ through a membrane. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. chain. Photosystems Where do the electrons that enter Photosystem II come from? The energy used to produce ATP in the light reactions of photosynthesis comes from _____. Since those early studies, the two light reactions have been separated in many ways, including separation of the membrane particles in which each reaction occurs. transport electrons from photosystem II to photosystem I: Definition. Where do the electrons entering photosystem II come from? Why? Molecular oxygen is produced during. Where do the electrons entering photosystem II come from? When manganese is selectively removed by chemical treatment, the thylakoids lose the capacity to oxidize water, but all other parts of the electron pathway remain intact. The energy used to produce ATP in the light reactions of photosynthesis comes from __________. H2O and photosystem II: Definition. 8. Where do the electrons entering photosystem II come from? Why does Photosystem II occur before Photosystem I??? a) the first product of carbon fixation in C4 plants is a 4-carbon compound instead of a 3-carbon compound. Of the following, which occurs during the Calvin Cycle? A. a) stroma b) thylakoids c) granum d) stomata e) mitochorndrion. The P 680 + of light reaction II is capable of taking electrons from water in the presence of appropriate catalysts. C) water. The reactions of the Calvin cycle are not directly dependent on light, but they usually do not occur at night. The light reactions of photosynthesis use chemiosmosis to produce ATP that will be used in the Calvin cycle. Photosystems What happens if there’s no water to replace the water 18 During photosynthesis in chloroplasts, O2 is produced from _____ via a series of reactions associated with _____. Each time a P680 or P700 molecule gives up an electron, it returns to its ground (unexcited) state, but with a positive charge due to the loss of the electron. The excited chlorophyll electrons are transferred from the electron acceptors of photosystem II to photosystem I through an electron transport chain. The Calvin cycle could not occur without the light reactions. During the Calvin cycle, what happens during the carbon fixation phase? (Concept 10.1) Your Answer: It helps produce ATP from the light reactions.Correct Answer: It forms NADPH to be used in the Calvin cycle. a) the calvin cycle incorporates each CO2 molecule, one at a time, by attaching it to a 5-carbon sugar (RuBP). The electrons of photosystem II are excited and transferred to electron carriers. Where do the electrons entering photosystem II come from? The general features of a widely accepted mechanism for photoelectron transfer, in which two light reactions (light reaction I and light reaction II) occur during the transfer of electrons from water to carbon dioxide, were proposed by Robert Hill and Fay Bendall in 1960. With both red and blue light together, the amount of oxygen evolved far exceeded the sum of that seen with blue and red light alone. From photosystem II, the excited electron travels along a series of proteins. Special quinones are next in the series. Electrons first travel through photosystem II and then photosystem I. During photosynthesis in chloroplasts, O 2 is produced from _____ via a series of reactions associated with: Term. Which of the following statements correctly describes the difference in carbon fixation between C3 and C4 plants? The manganese-protein complex gives up these electrons one at a time via an unidentified carrier to P680+, reducing it to P680. Water. The electrochemical gradient that drives this chemiosmosis is formed across which structure(s)? a) stroma. Where do the electrons entering photosystem II come from? Ring in the new year with a Britannica Membership, Factors that influence the rate of photosynthesis, Chloroplasts, the photosynthetic units of green plants, The process of photosynthesis: the light reactions, The process of photosynthesis: the conversion of light energy to ATP, The process of photosynthesis: carbon fixation and reduction, Carbon fixation via crassulacean acid metabolism (CAM). Water. These positively charged ions are extremely strong oxidizing agents that remove an electron from a suitable donor. Since two electrons were removed from P700, they have to be replaced. Of the following, which occurs during the Calvin cycle? Generating an Energy Carrier: ATP During which process is molecular oxygen produced in photosynthesis? The light reactions also produce __________ and __________. Where do the electrons entering photosystem II come from? It is now known that DCMU blocks the transfer of electrons between the first quinone and the plastoquinone pool in light reaction II. An early study by American biochemist Robert Emerson employed the algae Chlorella, which was illuminated with red light alone, with blue light alone, and with red and blue light at the same time. The P680+ of light reaction II is capable of taking electrons from water in the presence of appropriate catalysts. The light reactions of photosynthesis supply the Calvin cycle with __________. Within the photosystem, enzymes capture photons of light to energize electrons that are then transferred through a variety of coenzymes and cofactors to reduce plastoquinone to plastoquinol. 11. ATP is produced by other electron acceptors in the electron transport chain. Which of the following statements correctly describes the relationship between the light reactions and the Calvin cycle? This mechanism is based on the relative potential (in volts) of various cofactors of the electron-transfer chain to be oxidized or reduced. "Looking for a Similar Assignment? water. It was substantial with blue light alone but not with red light alone. ¡ The photosystems are named for the dates of discovery, not for which one goes first or second. Later, photosystem II was discovered and found to be earlier in the electron transport chain. In diagrams that describe the light reaction stage of photosynthesis, the actual photochemical steps are typically represented by two vertical arrows. Which of the following statements describes why this is the case? This splits the water molecule, generating oxygen and hydrogen ions. In light reaction I, electrons are passed on to iron-sulfur proteins in the lamellar membrane, after which the electrons flow to ferredoxin, a small water-soluble iron-sulfur protein. a. Light energy (indicated by wavy arrows) absorbed by photosystem II causes the formation of high-energy electrons, which are transferred along a series of acceptor molecules in an electron transport chain to photosystem I. Photosystem II obtains replacement electrons from water molecules, resulting in their split into hydrogen ions (H+) and oxygen atoms.