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  • bilayer
  • The free energy of a closed bilayer under the osmotic pressure Δ p {\displaystyle \Delta p} (the outer pressure minus the inner one) as: where dA and dV are the area element of the membrane and the volume element enclosed by the closed bilayer, respectively, and λ is the surface tension of the bilayer. (wikipedia.org)
  • The cell membranes of a variety of different bacteria, fungi, animal and plant cells contain aquaporins through which water can flow more rapidly into and out of the cell than by diffusing through the phospholipid bilayer. (wikipedia.org)
  • aqueous
  • Alkaline anion exchange membrane fuel cells (AAEMFCs) are functionally similar to AFCs, the difference being AAEMFCs employ a solid polymer electrolyte while AFCs use aqueous potassium hydroxide (KOH) as an electrolyte. (wikipedia.org)
  • Electrochemical reactions when hydrogen is the fuel At Anode: H2 + 2OH− → 2H2O + 2e− At cathode: O2 + 2H2O + 4e− → 4OH− Electrochemical reactions when methanol is the fuel At anode: CH3OH + 6OH− → CO2 + 5H2O + 6e- At cathode: 3/2O2 + 3H2O + 6e− → 6OH− The alkaline fuel cell used by NASA in 1960s for Apollo and Space Shuttle program generated electricity at nearly 70% efficiency using aqueous solution of KOH as an electrolyte. (wikipedia.org)
  • Membranes create enclosed compartments that are separate from the external environment, thus providing the cell with functionally specialized aqueous spaces. (wikipedia.org)
  • hydrophobic
  • The fluid mosaic model not only provided an accurate representation of membrane mechanics, it enhanced the study of hydrophobic forces, which would later develop into an essential descriptive limitation to describe biological macromolecules. (wikipedia.org)
  • Their theory was also incorrect in that it ascribed the barrier properties of the membrane to electrostatic repulsion from the protein layer rather than the energetic cost of crossing the hydrophobic core. (wikipedia.org)
  • fluid mosai
  • The paucimolecular model immediately became popular and it dominated cell membrane studies for the following 30 years, until it became rivaled by the fluid mosaic model of Singer and Nicolson (1972). (wikipedia.org)
  • Despite the numerous models of the cell membrane proposed prior to the fluid mosaic model, it remains the primary archetype for the cell membrane long after its inception in the 1970s. (wikipedia.org)
  • Of the numerous models that have been developed to describe the deformation of cell membranes, a widely accepted model is the fluid mosaic model proposed by Singer and Nicolson in 1972. (wikipedia.org)
  • proton
  • A proton exchange membrane fuel cell transforms the chemical energy liberated during the electrochemical reaction of hydrogen and oxygen to electrical energy, as opposed to the direct combustion of hydrogen and oxygen gases to produce thermal energy. (wikipedia.org)
  • There were various studies applied on the membrane of H.salinarum to decipher the mechanism of light-driven proton pump. (wikipedia.org)
  • Another kind of these light-driven proton pumps is Archaerhodopsin-2 (aR 2) which was found in the claret membrane of Halorubrum.sp. (wikipedia.org)
  • protons
  • This reduction half-cell reaction or oxygen reduction reaction (ORR) is represented by: At the cathode: Overall reaction: The reversible reaction is expressed in the equation and shows the reincorporation of the hydrogen protons and electrons together with the oxygen molecule and the formation of one water molecule. (wikipedia.org)
  • They drive the hyperpolarization of the cell membrane by secreting protons in presence of light. (wikipedia.org)
  • As the pH naturally neutralizes within the liposome (protons can pass through some membranes), the drug will also be neutralized, allowing it to freely pass through a membrane. (wikipedia.org)
  • cathode
  • The electrons travel along an external load circuit to the cathode side of the MEA, thus creating the current output of the fuel cell. (wikipedia.org)
  • Finally, the membrane must be resistant to the reducing environment at the cathode as well as the harsh oxidative environment at the anode. (wikipedia.org)
  • Water management is a very difficult subject in PEM systems, primarily because water in the membrane is attracted toward the cathode of the cell through polarization. (wikipedia.org)
  • Also, methanol crossover from anode to cathode is reduced in AAEMFCs compared to PEMFCs, due to the opposite direction of ion transport in the membrane, from cathode to anode. (wikipedia.org)
  • deformation
  • Normally, this deformation lasts only as long as a cell is present in a capillary, but in hereditary elliptocytosis the instability of the cytoskeleton means that erythrocytes deformed by passing through a capillary are forever rendered elliptical. (wikipedia.org)
  • bilayers
  • Rather than being made up of phospholipids, however, early membranes may have formed from monolayers or bilayers of fatty acids, which may have formed more readily in a prebiotic environment. (wikipedia.org)
  • 1991
  • Boman HG (1991), "Antibacterial peptides: key components needed in immunity", Cell, 65 (2): 205-207, doi:10.1016/0092-8674(91)90154-Q, PMID 2015623. (wikipedia.org)
  • metabolism
  • One of challenges in the investigation is to elucidate how faulty genes that are ubiquitously expressed and are involved in basic cellular functions, such as sphingolipid metabolism, maintenance of organellar integrity, membrane dynamics, and transcription regulation, affect specific populations of neurons. (wikipedia.org)
  • Mabel worked as a technician in the Medical Research Council Unit for Research in Cell Metabolism under Hans Krebs at the University of Sheffield from 1943 to 1946, and enrolled as a student in 1946, continuing to work for Krebs. (wikipedia.org)
  • structures
  • In addition, cell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signalling and serve as the attachment surface for several extracellular structures, including the cell wall, the carbohydrate layer called the glycocalyx, and the intracellular network of protein fibers called the cytoskeleton. (wikipedia.org)
  • In 1890, an update to the Cell Theory stated that cell membranes existed, but were merely secondary structures. (wikipedia.org)
  • intracellular
  • However, some microscopists correctly identified at this time that while invisible, it could be inferred that cell membranes existed in animal cells due to intracellular movement of components internally but not externally and that membranes weren't the equivalent of a cell wall to plant cell. (wikipedia.org)
  • Gastrin, stimulating CCK2 receptors (least significant contribution, but also causes histamine secretion by local ECL cells) Activation of histamine through H2 receptor causes increases intracellular cAMP level while Ach through M3 receptor and gastrin through CCK2 receptor increases intracellular calcium level. (wikipedia.org)
  • Regulation
  • They then showed that this metabolic response, which became known as the 'PI effect', occurred in a variety of stimulated tissues, such as pigeon pancreas (1958), suggesting that it plays a widespread role in cell regulation. (wikipedia.org)
  • hydrogen
  • The enzyme hydrogen potassium ATPase (H+/K+ ATPase) is unique to the parietal cells and transports the H+ against a concentration gradient of about 3 million to 1, which is the steepest ion gradient formed in the human body. (wikipedia.org)
  • bicarbonate
  • The absence of cations is, however, difficult to achieve, as most membranes are conditioned to functional hydroxide or bicarbonate forms out of their initial, chemically stable halogen form, and may significantly impact fuel cell performance by both competitively adsorbing to active sites and exerting Helmholtz-layer effects. (wikipedia.org)
  • The bicarbonate ion (HCO3−) is exchanged for a chloride ion (Cl−) on the basal side of the cell and the bicarbonate diffuses into the venous blood, leading to an alkaline tide phenomenon. (wikipedia.org)
  • extracellular
  • Traube had no direct evidence for the composition of this film, though, and incorrectly asserted that it was formed by an interfacial reaction of the cell protoplasm with the extracellular fluid. (wikipedia.org)
  • thickness
  • In an attempt to accept or reject the hypothesis, researchers measured membrane thickness. (wikipedia.org)
  • Independently, the leptoscope was invented in order to measure very thin membranes by comparing the intensity of light reflected from a sample to the intensity of a membrane standard of known thickness. (wikipedia.org)
  • endocytosis
  • This is accomplished by the fusion of canalicular precursors, or "tubulovesicles", with the membrane to increase surface area, and the reciprocal endocytosis of the canaliculi (reforming the tubulovesicles) to decrease it. (wikipedia.org)
  • Liposomes can also be decorated with opsonins and ligands to activate endocytosis in other cell types. (wikipedia.org)
  • known
  • Since the invention of the microscope in the seventeenth century it has been known that plant and animal tissue is composed of cells : the cell was discovered by Robert Hooke. (wikipedia.org)
  • The membrane must also not allow either gas to pass to the other side of the cell, a problem known as gas crossover. (wikipedia.org)
  • Alkaline anion exchange membrane fuel cells (AAEMFC) also known as hydroxide exchange membrane fuel cells (HEMFCs), anion-exchange membrane fuel cells (AEMFCs), or alkaline membrane fuel cells (AMFCs), are a type of alkaline fuel cells (AFCs). (wikipedia.org)
  • Hereditary elliptocytosis, also known as ovalocytosis, is an inherited blood disorder in which an abnormally large number of the patient's erythrocytes (i.e. red blood cells) are elliptical rather than the typical biconcave disc shape. (wikipedia.org)
  • The use of liposomes for transformation or transfection of DNA into a host cell is known as lipofection. (wikipedia.org)
  • However
  • However the first report of protein-mediated water transport through membranes was by Gheorghe Benga in 1986, prior to Agre's first publication on the topic. (wikipedia.org)
  • However, this did not explain how water could move so quickly through some cells. (wikipedia.org)
  • Theory
  • While Robert Hooke's discovery of cells in 1665 led to the proposal of the Cell Theory, Hooke misled the cell membrane theory that all cells contained a hard cell wall since only plant cells could be observed at the time. (wikipedia.org)
  • They interpreted this as meaning that to pass the cell membrane a molecule must be at least sparingly soluble in oil, their "lipoid theory of narcosis. (wikipedia.org)
  • researchers
  • His prediction was soon confirmed by the experiment Additionally, researchers obtained an analytical solution to (3) which explained the classical problem, the biconcave discoidal shape of normal red blood cells. (wikipedia.org)
  • Biochemistry
  • Mabel and Lowell summarized their cell membrane biochemistry research in a 1965 article in Scientific American. (wikipedia.org)
  • Interest in the PI effect waned in the 1960s and 1970s, but experienced a resurgence in the 1980s due to advances in technology and understanding of cell membrane biochemistry. (wikipedia.org)
  • Mabel and Lowell became regarded as founders of an important and still growing field of biochemistry and cell biology - the many roles of inositol phospholipids in cell function - for which they were honored at a 1996 symposium at the University of Wisconsin that gathered their colleagues from around the world. (wikipedia.org)
  • fuel cells
  • A March 2014 study by NASA's Jet Propulsion Laboratory demonstrated a unique way to study the origins of life: fuel cells. (wikipedia.org)
  • Thus
  • Thus the free energy density can be expressed as the invariant form of 2 H {\displaystyle 2H} , K {\displaystyle K} , t r ( ε ) {\displaystyle \mathrm {tr} (\varepsilon )} and det ( ε ) {\displaystyle \det(\varepsilon )} : where ε {\displaystyle \varepsilon } is the in-plane strain of the membrane skeleton. (wikipedia.org)
  • The pivotal part of the cell is the triple phase boundary (TPB) where the electrolyte, catalyst, and reactants mix and thus where the cell reactions actually occur. (wikipedia.org)
  • primarily
  • Gastrin primarily induces acid-secretion indirectly, increasing histamine synthesis in ECL cells,which in turn signal parietal cells via histamine release/H2 stimulation. (wikipedia.org)
  • similar
  • The plant cell wall was easily visible even with these early microscopes but no similar barrier was visible on animal cells, though it stood to reason that one must exist. (wikipedia.org)
  • surface
  • Since the surface tension values appeared to be much lower than would be expected for an oil-water interface, it was assumed that some substance was responsible for lowering the interfacial tensions in the surface of cells. (wikipedia.org)
  • When they compared the area of the monolayer to the surface area of the cells, they found a ratio of two to one. (wikipedia.org)
  • Hepsin is a cell surface serine protease. (wikipedia.org)
  • found
  • The cell membrane is the only cellular structure that is found in all of the cells of all of the organisms on Earth. (wikipedia.org)
  • Electrokinesis has also been observed in biology, where it was found to cause physical damage to neurons by inciting movement in their membranes. (wikipedia.org)
  • These cells are located in the gastric glands found in the lining of the fundus and in the body of the stomach. (wikipedia.org)
  • A canaliculus is an adaptation found on gastric parietal cells. (wikipedia.org)
  • presence
  • A reasonable number of unmyelinated axons remained, although the presence of stacks of flattened Schwann cell processes suggested unmyelinated axon loss. (wikipedia.org)
  • water
  • Operating temperatures above 100 °C are desired[citation needed] so the water byproduct becomes steam and water management becomes less critical in cell design. (wikipedia.org)
  • Water moves through cells in an organized way, most rapidly in tissues that have aquaporin water channels. (wikipedia.org)
  • For many years, scientists assumed that water leaked through the cell membrane, and some water does. (wikipedia.org)
  • made
  • Microscopists focused on the cell wall for well over 150 years until advances in microscopy were made. (wikipedia.org)
  • Based on this evidence and further experiments, they concluded that the cell membrane might be made of lecithin (phosphatidylcholine) and cholesterol. (wikipedia.org)
  • A more direct investigation of the membrane was made possible through the use of electron microscopy in the late 1950s. (wikipedia.org)
  • occurs
  • For instance, the most common genotype responsible for HPP occurs when the affected individual inherits an α-spectrin mutation from one parent (i.e. one parent has hereditary elliptocytosis) and the other parent passes on an as-yet-undefined defect that causes the affected individual's cells to preferentially produce the defective α-spectrin rather than normal α-spectrin. (wikipedia.org)
  • The longer hyperglycemia occurs in blood, the more glucose binds to hemoglobin in the red blood cells and the higher the glycated hemoglobin. (wikipedia.org)
  • receptors
  • In a new study published in Science Signaling, they identify how these receptors are activated in the cell membrane and the processes that are then triggered within the cell. (news-medical.net)
  • There are two general types of membrane proteins: transporters and receptors. (encyclopedia.com)
  • These receptors are increased in number on luminal side by fusion of tubulovesicles during activation of parietal cells and removed during deactivation. (wikipedia.org)
  • Parietal cells secrete acid in response to three types of stimuli: Histamine, stimulates H2 histamine receptors (most significant contribution). (wikipedia.org)
  • Gastrin, stimulating CCK2 receptors (least significant contribution, but also causes histamine secretion by local ECL cells) Activation of histamine through H2 receptor causes increases intracellular cAMP level while Ach through M3 receptor and gastrin through CCK2 receptor increases intracellular calcium level. (wikipedia.org)
  • These receptors are present on basolateral side of membrane. (wikipedia.org)
  • Schwann
  • A reasonable number of unmyelinated axons remained, although the presence of stacks of flattened Schwann cell processes suggested unmyelinated axon loss. (wikipedia.org)
  • fluid
  • The paucimolecular model immediately became popular and it dominated cell membrane studies for the following 30 years, until it became rivaled by the fluid mosaic model of Singer and Nicolson (1972). (wikipedia.org)
  • Despite the numerous models of the cell membrane proposed prior to the fluid mosaic model , it remains the primary archetype for the cell membrane long after its inception in the 1970s. (wikipedia.org)
  • Cohen, a Professor of Chemistry and Chemical Biology and of Physics, is the lead author of a new study that upends the conventional theories about the fluid nature of cell membranes and how they react to tension. (news-medical.net)
  • Traube had no direct evidence for the composition of this film, though, and incorrectly asserted that it was formed by an interfacial reaction of the cell protoplasm with the extracellular fluid. (wikipedia.org)
  • Based on these observations, Quincke asserted that the cell membrane comprised a fluid layer of fat less than 100 nm thick. (wikipedia.org)
  • Of the numerous models that have been developed to describe the deformation of cell membranes, a widely accepted model is the fluid mosaic model proposed by Singer and Nicolson in 1972. (wikipedia.org)
  • processes
  • Transport across the cell membrane underlies a variety of physiological processes, from the beating of an animal's heart to the opening of tiny pores in leaves that enables gas exchange with the environment. (newworldencyclopedia.org)
  • regulation
  • They then showed that this metabolic response, which became known as the 'PI effect', occurred in a variety of stimulated tissues, such as pigeon pancreas (1958), suggesting that it plays a widespread role in cell regulation. (wikipedia.org)
  • Electron
  • Firstly, the role of multi-domain cell surface proteins involved in cell recognition and secondly, the components of the electron-transport chain and its relation to energy transduction including an introduction to Mitchell's chemi-osmotic hypothesis. (southampton.ac.uk)
  • A more direct investigation of the membrane was made possible through the use of electron microscopy in the late 1950s. (wikipedia.org)
  • vesicles
  • Neal Devaraj, a chemistry and biochemistry professor at UC San Diego, leads a research team that develops and explores new reactions that can trigger the formation of membranes, particularly the spheres that characterize membranes that enclose vesicles and cells. (ucsd.edu)
  • Self-assembled vesicles are essential components of primitive cells. (wikipedia.org)
  • Eukaryotes
  • Higher-level cells known as eukaryotes contain specialized components, called organelles, that play dedicated roles in its growth and development. (encyclopedia.com)
  • polymer
  • Our goal is to develop a process to easily synthesize the polymer at scale, creating large area membranes for testing that are thinner than human hair. (udel.edu)
  • secretion
  • Gastrin primarily induces acid-secretion indirectly, increasing histamine synthesis in ECL cells,which in turn signal parietal cells via histamine release/H2 stimulation. (wikipedia.org)
  • reactions
  • The pivotal part of the cell is the triple phase boundary (TPB) where the electrolyte, catalyst, and reactants mix and thus where the cell reactions actually occur. (wikipedia.org)
  • Importantly, the membrane must not be electrically conductive so the half reactions do not mix. (wikipedia.org)
  • bound
  • In the early 19th century, cells were recognized as being separate entities, unconnected, and bound by individual cell walls after it was found that plant cells could be separated. (wikipedia.org)