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Photosystem I (PSI, or plastocyanin–ferredoxin oxidoreductase) is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I [ 1 ] is an integral membrane protein complex that uses light energy to catalyze the transfer of electrons across the thylakoid membrane from plastocyanin to ...
The cyclic light-dependent reactions occur only when the sole photosystem being used is photosystem I. Photosystem I excites electrons which then cycle from the transport protein, ferredoxin (Fd), to the cytochrome complex, b 6 f, to another transport protein, plastocyanin (Pc), and back to photosystem I. A proton gradient is created across the ...
One of the electrons of excited P680* will be transferred to a non-fluorescent molecule, which ionizes the chlorophyll and boosts its energy further, enough that it can split water in the oxygen evolving complex (OEC) of PSII and recover its electron. [citation needed] At the heart of the OEC are 4 Mn atoms, each of which can trap one electron ...
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
The different stages of mitosis altogether define the mitotic phase (M phase) of a cell cycle—the division of the mother cell into two daughter cells genetically identical to each other. [ 3 ] The process of mitosis is divided into stages corresponding to the completion of one set of activities and the start of the next.
Steps of the cell cycle. The G 2-M checkpoint occurs between the G 2 and M phases. G2-M arrest. The G 2-M DNA damage checkpoint is an important cell cycle checkpoint in eukaryotic organisms that ensures that cells don't initiate mitosis until damaged or incompletely replicated DNA is sufficiently repaired.
In eukaryotes, the cell cycle consists of four main stages: G 1, during which a cell is metabolically active and continuously grows; S phase, during which DNA replication takes place; G 2, during which cell growth continues and the cell synthesizes various proteins in preparation for division; and the M phase, during which the duplicated ...
Photosystem II is present on the thylakoid membranes inside chloroplasts, the site of photosynthesis in green plants. [9] The structure of Photosystem II is remarkably similar to the bacterial reaction center, and it is theorized that they share a common ancestor. The core of Photosystem II consists of two subunits referred to as D1 and D2 ...