Structural units of protein involved in photosynthesis
Light-dependent reactions of photosynthesis at the thylakoid membrane
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.
PSII will absorb red light, and PSI will absorb far-red light. Although photosynthetic activity will be detected when the photosystems are exposed to either red or far-red light, the photosynthetic activity will be the greatest when plants are exposed to both wavelengths of light. Studies have actually demonstrated that the two wavelengths together have a synergistic effect on the photosynthetic activity, rather than an additive one.[1]
Each photosystem has two parts: a reaction center, where the photochemistry occurs, and an antenna complex, which surrounds the reaction center. The antenna complex contains hundreds of chlorophyll molecules which funnel the excitation energy to the center of the photosystem. At the reaction center, the energy will be trapped and transferred to produce a high energy molecule.[2]
The main function of PSII is to efficiently split water into oxygen molecules and protons. PSII will provide a steady stream of electrons to PSI, which will boost these in energy and transfer them to NADP+ and H+ to make NADPH. The hydrogen from this NADPH can then be used in a number of different processes within the plant.[2]
^Zhen, Shuyang; Van Iersel, Marc W. (2017-02-01). "Far-red light is needed for efficient photochemistry and photosynthesis". Journal of Plant Physiology. 209: 115–122. doi:10.1016/j.jplph.2016.12.004. ISSN 0176-1617. PMID 28039776.
^ abTaiz, Lincoln (2018). Fundamentals of plant physiology. ISBN 978-1-60535-790-4. OCLC 1035316853.
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of...
Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and...
Photosystem II (or water-plastoquinone oxidoreductase) is the first protein complex in the light-dependent reactions of oxygenic photosynthesis. It is...
cell walls, is less absorbed. Two types of chlorophyll exist in the photosystems of green plants: chlorophyll a and b. Chlorophyll was first isolated...
(P700) of photosystem I are replaced by transfer from plastocyanin, whose electrons come from electron transport through photosystem II. Photosystem II, as...
first electron carrier intermediate in the electron transfer pathway of Photosystem II (PS II) in plants, and the type II photosynthetic reaction center...
P680, or photosystem II primary donor, is the reaction-center chlorophyll a molecular dimer associated with photosystem II in plants, algae, and cyanobacteria...
membrane: Photosystems I and II Cytochrome b6f complex ATP synthase Photosystem II is located mostly in the grana thylakoids, whereas photosystem I and ATP...
that are part of larger supercomplexes known as P700 in Photosystem I and P680 in Photosystem II. The structures of these supercomplexes are large, involving...
in photosystem II. The electrons are used to reduce carbon dioxide, which eventually becomes incorporated into sugars. Photo-excitation o photosystem I...
P700, or photosystem I primary donor, is the reaction-center chlorophyll a molecular dimer associated with photosystem I in plants, algae, and cyanobacteria...
quantasome is thought to represent the site of photosystem I, the larger to represent the site of photosystem II.[clarification needed] Light-dependent reactions...
thylakoid. Plastoquinone is reduced when it accepts two electrons from photosystem II and two hydrogen cations (H+) from the stroma of the chloroplast,...
in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic...
P700, a pigment in a complex called photosystem I, flows in a cyclic pathway. The electron starts in photosystem I, passes from the primary electron acceptor...
molecules are located in both photosystem II and photosystem I. They are known as P680 for Photosystem II and P700 for Photosystem I. P680 and P700 are the...
chloroplasts in cyanobacteria and plants. More specifically, it is located in Photosystem II (PSII) and in the light-harvesting complex II (LHCII). Ycf9 acts as...
photosynthesis component light-dependent reactions is referred to as photosystem II. The complex utilizes an enzyme to capture photons of light, providing...
complex is one step along the chain that transfers electrons from Photosystem II to Photosystem I, and at the same time pumps protons into the thylakoid space...
around photosystem II contain the majority of chlorophyll b. Hence, in shade-adapted chloroplasts, which have an increased ratio of photosystem II to photosystem...
(diuron) are photosystem II inhibitors. Other members of this class are chlorbromuron, pyrazon, isoproturon, bromacil, and terbacil. Photosystem I inhibitors...
680 for its absorption maximum at 680 nm) in the reaction center of photosystem II via resonance energy transfer. P680 can also directly absorb a photon...
photosynthesis. In this stage, photons are absorbed by the membrane-bound photosystems. Photosystems contain two major domains, the light-harvesting complex (antennae)...
oxygen-evolving complex (OEC), containing four atoms of manganese, is a part of photosystem II contained in the thylakoid membranes of chloroplasts. The OEC is responsible...
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