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Chemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient. An important example is the formation of adenosine triphosphate (ATP) by the movement of hydrogen ions (H +) across a membrane during cellular respiration or photosynthesis. An ion gradient has potential energy and can be ...
Bacteriorhodopsin (Bop) is a protein used by Archaea, most notably by haloarchaea, a class of the Euryarchaeota. [1] It acts as a proton pump; that is, it captures light energy and uses it to move protons across the membrane out of the cell. [2] The resulting proton gradient is subsequently converted into chemical energy.
The equilibrium dynamics of Complex I are primarily driven by the quinone redox cycle. In conditions of high proton motive force (and accordingly, a ubiquinol-concentrated pool), the enzyme runs in the reverse direction. Ubiquinol is oxidized to ubiquinone, and the resulting released protons reduce the proton motive force. [14]
The overall structure and the catalytic mechanism of the chloroplast ATP synthase are almost the same as those of the bacterial enzyme. However, in chloroplasts, the proton motive force is generated not by respiratory electron transport chain but by primary photosynthetic proteins. The synthase has a 40-aa insert in the gamma-subunit to inhibit ...
A proton motive force is generated using only the quinone pool. In heliobacteria, Green sulfur, and Green non-sulfur bacteria, NADH is formed using the protein ferredoxin, an energetically favorable reaction. In purple bacteria, NADH is formed by reverse electron flow due to the lower chemical potential of this reaction center.
Symporter. A symporter is an integral membrane protein that is involved in the transport of two (or more) different molecules across the cell membrane in the same direction. The symporter works in the plasma membrane and molecules are transported across the cell membrane at the same time, and is, therefore, a type of cotransporter.
In all living organisms, a series of redox reactions is used to produce a transmembrane electrochemical potential gradient, or a so-called proton motive force (pmf). Redox reactions are chemical reactions in which electrons are transferred from a donor molecule to an acceptor molecule. The underlying force driving these reactions is the Gibbs ...
An uncoupler or uncoupling agent is a molecule that disrupts oxidative phosphorylation in prokaryotes and mitochondria or photophosphorylation in chloroplasts and cyanobacteria by dissociating the reactions of ATP synthesis from the electron transport chain. The result is that the cell or mitochondrion expends energy to generate a proton-motive ...