This article is about proton pumps in general. For the proton P-type ATPase, see proton ATPase. This article is about the H+-ATPase For the H+/K+ ATPase see Hydrogen potassium ATPase.

Proton gradient: Pink represents the matrix while the red dots represent protons.

A proton pump is an integral membrane protein that is capable of moving protons across the membrane of a cell, mitochondrion, or other subcellular compartment. An Integral Membrane Protein ( IMP) is a Protein Molecule (or assembly of proteins that is permanently attached to the Biological membrane. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells.

Function

In cell respiration, the pumps grab protons from the matrix, the space between the two enclosing membranes of the organelle, and release the protons within the inner membrane. Cellular respiration is the set of the metabolic reactions and processes that take place in Organisms cells to convert biochemical energy from In Biology, matrix (plural matrices) is the material between animal or plant cells, the material (or tissue in which more specialized structures are embedded In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed The confined protons create a difference or gradient in both pH and electric charge (ignoring differences in buffer capacity) and establish an electrochemical potential that acts as a kind of battery or reservoir of stored energy for the cell. In Vector calculus, the gradient of a Scalar field is a Vector field which points in the direction of the greatest rate of increase of the scalar pH is the measure of the acidity or alkalinity of a Solution. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. For an aqueous solution composed of both a weak acid or base and its conjugate see Buffer solution. In Electrochemistry, the electrochemical potential, \bar{\mu} sometimes confusingly abbreviated to ECP is a Thermodynamic measure that combines the The inner cell membrane functions in a similar way to a dam in a river. It blocks protons from drifting back into the matrix. Since the pumping action is against the gradient, it requires work (energy). In Physics, mechanical work is the amount of Energy transferred by a Force. The process is directly analogous to bicycling uphill or charging a battery (storing up potential energy). Potential energy can be thought of as Energy stored within a physical system It is important to remember that the proton pump does not create energy. Instead, the gradient stores energy for the appropriate time.

Mobility

Some of the enzymes involved in the electron transport chain, such as ubiquinone, travel along the matrix, like freight boats, navigating up and down the river. An electron transport chain couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer Coenzyme Q10 (also known as ubiquinone ubidecarenone coenzyme Q and abbreviated at times to CoQ10 CoQ Q10 or Q is a Benzoquinone, where Q

Others such as NADH-Q reductase, act like ferryboats and cross the matrix. Nicotinamide adenine dinucleotide, abbreviated NAD+, is a Coenzyme found in all living cells The compound is a dinucleotide since it consists A reductase is an Enzyme which lowers the Activation energy for a reduction reaction. Enzymes that can cross the matrix may have a secondary role as proton pumps because they can deliver protons to the inner membrane.

Diversity

In humans

In mitochondria, reducing equivalents provided by electron transfer or photosynthesis power this translocation of protons. In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Electrochemistry is a branch of Chemistry that studies Chemical reactions which take place in a Solution at the interface of an electron conductor An electron transport chain couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. For example, the translocation of protons by cytochrome c oxidase is powered by reducing equivalents provided by reduced cytochrome c. The Enzyme cytochrome c oxidase or Complex IV () is a large Transmembrane protein complex found in Bacteria and the Mitochondrion Cytochrome c, or cyt c (horse heart PDB 1HRC is a small Heme Protein found loosely associated with the inner membrane In the plasma membrane proton ATPase and in the ATPase proton pumps of other cellular membranes, ATP itself powers this transport. The cell membrane (also called the plasma membrane, plasmalemma, or "phospholipid bilayer" is a Selectively permeable Lipid bilayer ATPases are a class of Enzymes that catalyze the Decomposition of Adenosine triphosphate (ATP into Adenosine diphosphate (ADP and

The F_oF₁ ATP synthase of mitochondria, in contrast, usually conduct protons from high to low concentration across the membrane while drawing energy from this flow to synthesize ATP. An ATP synthase ( is a general term for an Enzyme that can synthesize Adenosine triphosphate (ATP from Adenosine diphosphate (ADP and inorganic To allow the passage of protons a proton channel temporarily opens in the inner membrane. Ion channels are pore-forming Proteins that help establish and control the small Voltage Gradient across the Plasma membrane of all living

Non-humans

In bacteria and other ATP-producing organelles than mitochondria, ATP-producing organelles, reducing equivalents provided by electron transfer or photosynthesis power the translocation of protons. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Electrochemistry is a branch of Chemistry that studies Chemical reactions which take place in a Solution at the interface of an electron conductor An electron transport chain couples a chemical reaction between an electron donor (such as NADH) and an electron acceptor (such as O2) to the transfer Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy.

CF₁ ATP ligase of chloroplasts correspond to the human F_oF₁ ATP synthase in plants. In Biochemistry, a ligase (from the Latin verb ligāre &mdash "to bind" or "to glue together" is an Enzyme that can catalyse Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis.

Bacteriorhodopsin is a photosynthetic pigment used by archaea, most notably halobacteria. Bacteriorhodopsin is a protein used by Archaea, most notably Halobacteria. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. For the drug referred to as "pigment" see Black tar heroin. Note The word "halobacteria" is also the plural form of the word " Halobacterium "

See also

• transmembrane ATPase
• active transport
• cytochrome
• mitochondrion
• chloroplast
• electron transfer chain
• proton pump inhibitor
• ATP synthase
• V-ATPase
• GORD
• Kidney
• proton ATPase

External links

• MeSH Proton+Pumps