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Other forms of chlorophyll exist, such as the accessory pigments chlorophyll b, chlorophyll c, chlorophyll d, [12] and chlorophyll f. Chlorophyll b is an olive green pigment found only in the chloroplasts of plants , green algae , any secondary chloroplasts obtained through the secondary endosymbiosis of a green alga, and a few cyanobacteria ...
The oxidation of water is catalyzed in photosystem II by a redox-active structure that contains four manganese ions and a calcium ion; this oxygen-evolving complex binds two water molecules and contains the four oxidizing equivalents that are used to drive the water-oxidizing reaction (Kok's S-state diagrams).
The process of oxidizing two molecules of water to form an oxygen molecule requires four electrons. The water molecules that are oxidized in the manganese center are the source of the electrons that reduce the two molecules of Q to QH 2. To date, this water splitting catalytic center has not been reproduced by any man-made catalyst.
[2] Many types of plant cells contain a large central vacuole, a water-filled volume enclosed by a membrane known as the tonoplast [3] that maintains the cell's turgor, controls movement of molecules between the cytosol and sap, stores useful material such as phosphorus and nitrogen [4] and digests waste proteins and organelles.
Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. [2] Its name is derived from the Greek words χλωρός (khloros, "pale green") and φύλλον (phyllon, "leaf"). [3] Chlorophyll allows plants to absorb energy from light.
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.
The water-splitting reaction occurs on the lumenal side of the thylakoid membrane and is driven by the light energy captured by the photosystems. This oxidation of water conveniently produces the waste product O 2 that is vital for cellular respiration. The molecular oxygen formed by the reaction is released into the atmosphere.
In land plants, the plastids that contain chlorophyll can perform photosynthesis, thereby creating internal chemical energy from external sunlight energy while capturing carbon from Earth's atmosphere and furnishing the atmosphere with life-giving oxygen. These are the chlorophyll-plastids—and they are named chloroplasts; (see top graphic).