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Sodium-Potassium pump, an example of Primary active transport
Sodium-Potassium pump, an example of Primary active transport

Active transport (sometimes called active intake because of the absorbing movement of particles) is an energy-requiring process that moves material across a cell membrane and up the concentration gradient. The cell uses active transport in three situations: when a particle is going from low to high concentration, when particles need help entering the membrane because they are selectively impermeable, and when very large particles enter and exit the cell.

Active transport is the mediated process of moving molecules and other substances across membranes. Use this tutorial to learn about active transport, including such key terms as adenosine triphosphate (ATP), carrier mediated transport, and concentration gradients.

When particles are being moved from areas of low concentration to areas of high concentration(ie. against the concentration gradient) then specific carrier proteins in the membrane are required to move these particles. the carrier proteins bind to specific molecules (eg. glucose) and transport them into the cell where they are released. Energy is required for this process so this is known as Active Transport. Examples: sodium is transported out of the cell and potassium into the cell by the sodium/potassium pump, a form of active transport.


Active transport can be:

Primary: Uses the chemical energy from ATP or other sources.

or

Secondary: Uses the electrochemical gradient to power transport. In Cellular biology, an electrochemical gradient is a spatial variation of both Electrical potential and chemical Concentration across a membrane


Contents

Classes of primary transporters (pumps)

ABC pumps

ABC class pumps transport small molecules across membranes. ATP-binding cassette transporters ( ABC-transporter) are members of a superfamily that is one of the largest and most ancient families with representatives in all extant They are also called the ABC superfamily. They consist of two transmembrane domains, and two ATP binding domains. ABC pumps are involved in the transport of small molecules, phospholipids and lipophilic drugs in mammalian cells. Phospholipids are a class of Lipids and are a major component of all Biological membranes All phospholipids contain a Diglyceride, a Phosphate Lipophilicity, fat-liking, refers to the ability of a Chemical compound to dissolve in fats oils lipids and non-polar solvents such as Hexane or Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands In bacteria they transport amino acids, sugars and peptides. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this Peptides (from the Greek πεπτίδια, "small digestibles" are short Polymers formed from the linking in a defined order of α- Amino [1]

P-type pumps

P-type pumps use ATP to transport ions against a gradient. P-type (or E1-E2-type ATPases constitute a superfamily of cation transport enzymes present both in prokaryota and eukaryota whose members mediate membrane flux of all common biologically An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge They are phosphorylated during transport, which is different from the other classes of active transport pumps. Phosphorylation is the addition of a Phosphate (PO4 group to a Protein molecule or a small molecule

Some examples of P-class pumps are the sodium-potassium pump, proton pump, calcium transport in muscle cells and the hydrogen-potassium pump in the apical membrane of the stomach. This article is about the H+-ATPase For the H+/K+ ATPase see Hydrogen potassium ATPase. Calcium ATPase is a form of P-ATPase which transfers Calcium after a Muscle has contracted Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the Gastric hydrogen potassium ATPase is also known as H+/K+ ATPase Function and location The gastric hydrogen potassium ATPase or In Human anatomy, the stomach is a J-shaped hollow muscular organ of the Gastrointestinal tract involved in the second phase of Digestion, following

V-type pumps

A V-Class Proton Pump moves protons from one side of a membrane to the other and uses ATP as the source of energy.
A V-Class Proton Pump moves protons from one side of a membrane to the other and uses ATP as the source of energy.

V-class proton pumps are a type of ATPase. Vacuolar type H+-ATPase ( V-ATPase) is a highly conserved evolutionarily ancient Enzyme with remarkably diverse functions in eukaryotic organisms ATPases are a class of Enzymes that catalyze the Decomposition of Adenosine triphosphate (ATP into Adenosine diphosphate (ADP and They use the energy released by the hydrolysis of ATP to move protons (or in a few cases of bacteria sodium-ions[2]) against their concentration gradient. Hydrolysis is a Chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Sodium (ˈsoʊdiəm is an element which has the symbol Na( Latin natrium, from Arabic natrun) atomic number 11 atomic mass 22 [3] All proteins that fall into this class have two structural domains. A protein domain is a part of protein sequence and structure that can evolve, function and exist independently of the rest of the protein chain One domain called the V0 domain is made of 5 subunits and is involved in translocation of the protein. This article deals with protein targeting in Eukaryotes except where noted The other domain is called the V1 domain which is composed of 8 subunits and is involved in ATP-hydrolysis. ATP hydrolysis is the reaction by which chemical energy that has been stored and transported in the high-energy phosphoanhydridic bonds in ATP (Adenosine triphosphate [4]

V-class proton pumps are found in a wide variety of organelle membranes. 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 In fungi, yeast and plant cells they are found in Vacuole membranes. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described Plant cells are eukaryotic cells that differ in several key respects from the cells of other eukaryotic Organisms Their distinctive features In general vacuole functions include Removing unwanted structural debris Isolating materials that might be harmful or a threat to the cell Containing In animals they are found in the membranes of lysosomes and endosomes. Lysosomes are Organelles that contain Digestive enzymes (acid Hydrolases. In Biology, an endosome is a membrane-bound compartment inside cells roughly 300-400 nm in diameter when fully mature V-class proton pumps are also found in the plasma membranes of macrophages[5] , osteoclasts[6] , and renal intercalated cells. Macrophages ( Greek: "big eaters" from makros "large" + phagein "eat" ( Mø) are cells within the tissues that An osteoclast (from the Greek words for "bone" and "broken" is a type of Bone cell that removes Bone tissue by removing its Mineralized matrix The kidneys are complicated organs that have numerous biological roles [7]

The function of this class of pump is strictly to transport protons across the membrane that they are embedded within. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Transporting protons across a membrane can decrease the pH on one side of the membrane which can be critical for organelle functioning. pH is the measure of the acidity or alkalinity of a Solution. [3] This is indeed the case in endosomes. When endosomes bud off from the plasma membrane as they do in receptor-mediated endocytosis V-class pumps increase the acidity within the lumen of the endosome. Receptor-mediated endocytosis (RME also called clathrin-dependent endocytosis, is a process by which cells internalize molecules ( Endocytosis) by the inward budding In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are A lumen (Lat lūmen, an opening or light (pl lumina is the inside space or lining of a tubular structure such as an artery or intestine This increased acidity acts as a signal to the ligand-receptors to release their ligands which can be molecules such as LDL or insulin. In Biochemistry, a receptor is a Protein molecule embedded in either the Plasma membrane or Cytoplasm of a cell to which a mobile signaling In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally Low-density lipoprotein ( LDL) is a type of Lipoprotein that transports Cholesterol and Triglycerides from the Liver to peripheral Insulin is a Hormone with intensive effects on both metabolism and several other body systems (eg vascular compliance Ligand release is critical so the ligand-receptors can be recycled back to the plasma membrane and join another endosome. [8] Decreasing the pH of endosomes is also important for the entry of some membrane bound viruses. A virus (from the Latin virus meaning Toxin or Poison) is a sub-microscopic infectious agent that is unable The viral protein haemagglutinin is located on the surface of the Influenza virus and the acidification provided by this protein aids in viral entry. Hemagglutinin (HA or haemagglutinin ( British English) is an Antigenic Glycoprotein found on the surface of the Influenza Viruses [9]

V-class pumps located in cell membranes which also have critical functions to the cell. In renal intercalated cells these pumps secrete protons into the fluid in the kidneys, helping to maintain an optimal pH in the kidneys. [10] In humans, mutations in the genes coding for this protein can lead to metabolic acidosis;[11] a potentially deadly disease. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism In Medicine, metabolic acidosis is a process which if unchecked leads to acidemia (i A disease is an abnormal condition of an organism that impairs bodily functions and can be deadly

F-type proton pumps

Uses H+ gradient in order to produce ATP. Can also work in the reverse direction.

Role in neurons

See also

References

  1. ^ Lodish et al (2008) Molecular Cell Biology, 6, W. Ion channels are pore-forming Proteins that help establish and control the small Voltage Gradient across the Plasma membrane of all living A symporter is an Integral membrane protein that is involved in movement of two or more different molecules or ions across a phospholipid membrane such as the Plasma membrane An antiporter (also called exchanger or counter-transporter) is an Integral membrane protein which is involved in Secondary active transport Passive transport means moving biochemicals and atomic or molecular substances across the Cell membrane. Osmosis is the Diffusion of a solvent (frequently water through a semi-permeable membrane, from a solution of low solute concentration (high water potential H. Freeman
  2. ^ Murata T, Yamato I, Kakinuma Y, Leslie AG, Walker JE (April 2005). "Structure of the rotor of the V-Type Na+-ATPase from Enterococcus hirae". Science (journal) 308 (5722): 654–9. doi:10.1126/science.1110064. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 15802565.  
  3. ^ a b Lodish, Harvey; et al. (2003). Molecular Cell Biology, 5, W. H. Freeman. ISBN 0716743663.  
  4. ^ Nishi, T. "The Vacuolar H+-ATPases - Nature's Most Versatile Proton Pumps". Nature Rev. MCB 3: 94-103.  
  5. ^ Brisseau, G. F. ; et al. (1996). "IL-1 increases V-ATPase activity in murine peritoneal macrophages". J. Biol. Chem 271: 2005-2001.  
  6. ^ Li, Y. P. ; Y. Liang, E. Li, P. Stashenko (1999). "Atp6i-deficient mice exhibit severe osteopetrosis due to loss of osteoclast-mediated extracellular acidification". Nature Genet. 23: 447-451.  
  7. ^ Brown, D. ; S. Breton (2000). "V-ATPase dependent lumenal acidification in the kidney collecting duct and the epididymis/vas deferens". J. Exp. Biol 203: 127-145.  
  8. ^ Forjac, M. (1999). "Structure and Properties of the Vacuolar (H+)-ATPases". J. Biol. .  
  9. ^ Han, X. ; Bushweller, J. H. , Cafiso, D. S. & Tamm, L. K. (2001). "Membrane structure and fusion-triggering conformational change of the fusion domain from influenza hemagglutinin". Nature Struct. Biol. 8: 715-720.  
  10. ^ Brown, Dennis\coauthors=Brenton, Sylvie (2000). "H+V-ATPase-Dependent Luminal Acidification in the Kidney Collecting Duct and Epididymis/Vas Deferens: Vesicle Recycling and Transcytotic Pathways". J. Exp. Biol. 203: 137-145.  
  11. ^ Karet, F. E; et al. (1999). "Mutations in ATP6N1B, encoding a new kidney vacuolar proton pump 116-kD subunit, cause recessive distal renal tubular acidosis with preserved hearing". Nature Genet. 21: 84-90.  
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