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Topic: Plasma membrane

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  Molecular Expressions Cell Biology: Plasma Membrane
The plasma membrane is permeable to specific molecules, however, and allows nutrients and other essential elements to enter the cell and waste materials to leave the cell.
In each layer of a plasma membrane, the hydrophobic lipid tails are oriented inwards and the hydrophilic phosphate groups are aligned so they face outwards, either toward the aqueous cytosol of the cell or the outside environment.
In prokaryotes and plants, the plasma membrane is an inner layer of protection since a rigid cell wall forms the outside boundary for their cells.
micro.magnet.fsu.edu /cells/plasmamembrane/plasmamembrane.html   (792 words)

 Cell Membranes
The plasma membrane serves as the interface between the machinery in the interior of the cell and the extracellular fluid (ECF) that bathes all cells.
Some of the proteins exposed at the interior face of the plasma membrane are tethered to cytoskeletal elements like actin microfilaments.
Some proteins are the exterior face of the plasma membrane are anchored to components of the extracellular matrix like collagen.
users.rcn.com /jkimball.ma.ultranet/BiologyPages/C/CellMembranes.html   (446 words)

  Plasma Membrane
The plasma membrane is classified as an organelle of the cell.
The surfaces of plasma membranes are generally studded with proteins that perform different functions, like the reception of nutrients or the anchoring of the flagellum.
The structure of the plasma membrane is often referred to as a fluid mosaic because it is a two-dimensional fluid (like a soap bubble) of freely diffusing lipids that is dotted with proteins.
www.iscid.org /encyclopedia/Plasma_Membrane   (321 words)

 Plasma Membrane - Picture - MSN Encarta
The plasma membrane that surrounds eukaryotic cells is a dynamic structure composed of two layers of phospholipid molecules interspersed with cholesterol and proteins.
The water-attracting heads anchor the membrane to the cytoplasm, the watery fluid inside the cell, and also to the water surrounding the cell.
Cholesterol molecules in the plasma membrane act as stabilizers that limit the movement of the two slippery phospholipids layers, which slide back and forth in the membrane.
encarta.msn.com /media_461547459/Plasma_Membrane.html   (281 words)

 Structure of the Plasma Membrane
The outer leaflet of the plasma membrane consists mainly of phosphatidylcholine and sphingomyelin, whereas phosphatidylethanolamine and phosphatidylserine are the predominant phospholipids of the inner leaflet.
It is noteworthy that many of the proteins anchored in the inner leaflet of the plasma membrane (including the Src and Ras proteins illustrated in Figure 12.10) play important roles in the transmission of signals from cell surface receptors to intracellular targets, as discussed in the next chapter.
Membrane proteins and phospholipids are unable to move back and forth between the inner and outer leaflets of the membrane at an appreciable rate.
www.ncbi.nlm.nih.gov /books/bv.fcgi?rid=cooper.section.1967   (3093 words)
For example, the combined membrane surface area of the endoplasmic reticulum (Section is 44 times larger than the plasma membrane surface area for a typical human cell (Table 8.17).
Integral membrane proteins are closely associated with membrane lipids and cannot be extracted from the membrane without disrupting the lipid bilayer.
For example, in the red blood cell membrane, glycophorin spans the entire membrane, all glycolipids and most of the phosphatidylcholine are in the outer monolayer, and the majority of the phosphatidylethanolamine and phosphatidylserine molecules are in the inner monolayer where most of the proteins reside.
www.nanomedicine.com /NMI/   (1638 words)

 Membrane Structure and Function
Membranes are vital because they separate the cell from the outside world.
Plasma membranes of human red blood cells and mouse liver contain nearly equal amounts of proteins (44, 49% respectively) and lipids (43, 52% respectively).
Plasma membranes have nearly one cholesterol per phospholipid molecule.
www.cytochemistry.net /Cell-biology/membrane_intro.htm   (1742 words)

 Brain and Behavior (IPHY 3730), University of Colorado at Boulder
The plasma membrane of a nerve cell functions as a barrier between the cytoplasm and the extracellular environment of the cell.
Membrane proteins in a nerve cell have a number of specific functions, such as permitting selective passive of an ion (=ion channel), moving an ion against a concentration gradient (=ion pump), or acting as a receptor which communicates information about events in the immediate environment.
Membrane transport of solute (such as glucose or Na+) is by either diffusion (passive, down a concentration gradient), facilitated diffusion (passive, mediated, down a concentration gradient, or active transport (requiring energy, mediated, but movement against a concentration gradient).
www.colorado.edu /kines/Class/IPHY3730/03plasmamembrane.html   (1723 words)

 Research at Plant Biochemistry
This enzyme pumps protons across the plasma membrane and thereby generates the proton and electrical gradient that is the driving force for secondary active transport executed by carriers and channels.
We have shown that proton pumping is activated by phosphorylation of a threonine residue in the C terminus of the enzyme and concomitant binding of a regulatory protein (a 14-3-3 protein) to the phosphorylated threonine residue.
We have shown that aquaporins may constitute up to 30% of the total protein of both the plasma membrane and the vacuolar membrane, and that water flow through an aquaporin may be regulated by phosphorylation of the protein.
www.plantbio.lu.se /research.html   (898 words)

 Plasma Membrane1
Image of Plasma Membrane - A large cartoon image of a cell membrane, followed by an in depth discussion on each component making up the membrane, the chemical compounds present, and the mechanisms which the plasma membrane carries out.
Membranes - Provides a cartoon like illustration of a plasma membrane, accompanied by important notes on the different structures making up, and the functions of, the membrane.
The plasma membrane forms a small pocket or infolding around the material to be internalized.
darwin.nmsu.edu /~molbio/cell/PM.html   (1098 words)

 The Plasma Membrane   (Site not responding. Last check: )
The generation (development) of the plasma membrane was a crucial step in the generation of the earliest forms of life without it cellular life is impossible.
All cell membranes are dynamic, fluid structures: most of their lipids and proteins are able to move about rapidly in the plane of the membrane.
Membrane proteins may be associated with the lipid bilayer in one of three ways.
io.uwinnipeg.ca /~simmons/1115/cm1503/plasmamembrane.htm   (322 words)

 NDI Terminology - membrane   (Site not responding. Last check: )
plasma membrane - The structure enveloping a cell, enclosing the cytoplasm, and forming a selective permeability barrier; it consists of lipids, proteins, and some carbohydrates, the lipids thought to form a bilayer in which integral proteins are embedded to varying degrees.
postsynaptic membrane - The area of plasma membrane of a postsynaptic cell, either a muscle fiber or a neuron, that is within the synapse and has areas especially adapted for receiving neurotransmitters.
presynaptic membrane - The area of the plasma membrane of a presynaptic axon that is within the synapse and has sites (active zones) especially adapted for the release of neurotransmitters.
www.ndif.org /Terms/membrane.html   (165 words)

 Plasma membrane and muscle innervation
The plasma membrane functions to maintain gradients–electrical and concentration–as well to control movements of various ions and other substances.
The fluid-mosaic model (1972) describes the membrane as a fluid double layer, or bilayer, composed mainly of phospholipids, cholesterol, and proteins.
Membrane potentials are created by a small number of negatively charged ions (anions) that have accumulated immediately to the inside of the membrane and a number of positively charged ions (cations) that have accumulated immediately to the outside of the membrane.
www-rohan.sdsu.edu /~ens632/plasmamembraneAP.htm   (960 words)

 UCMP Glossary: Cell biology
The cell consists primarily of an outer plasma membrane, which separates it from the environment; the genetic material (DNA), which encodes heritable information for the maintainance of life; and the cytoplasm, a heterogeneous assemblage of ions, molecules, and fluid.
Plants are known for their cell walls of cellulose, as are the green algae and certain protists, while fungi have cell walls of chitin.
This is believed to be the result of endosymbiosis, with the outer membrane coming from the eukaryotic cell, and the inner membrane belonging to the original prokaryote which was "swallowed".
www.ucmp.berkeley.edu /glossary/gloss4cell.html   (1470 words)

Membranes separate and maintain the chemical environments of the two sides of the membrane.
The beta-subunit is a glycoprotein, with the carbohydrate on the external surface of the membrane.
The receptor-insulin complex migrates to a region of the plasma membrane with the protein clathrin coating its inner surface.
library.med.utah.edu /NetBiochem/membrane.htm   (2845 words)

 Plasma Membrane | World of Biology
The plasma membrane is a very thin, continuous sheet of phospholipids and proteins that surrounds all living cells and separates them from their external environment.
In spite of its thinness, however, the plasma membrane is surprisingly strong, flexible, and stretchable.
Structurally, almost all plasma membranes are composed of a double layer of phospholipid molecules arranged with their hydrophobic (water-hating) lipid tails oriented toward the membrane interior and their hydrophilic (water-loving) heads making up the opposing membrane surfaces.
www.bookrags.com /research/plasma-membrane-wob   (261 words)

 Functions of the Plasma Membrane
The cell's plasma membrane does not simply form a "sack" in which to keep all the cytoplasm and other cellular organelles.
The plasma membrane is a very important structure which functions to allow certain substances to enter or leave the cell.
Both the protein portion and the phospholipid portion of the membrane are involved in the permeability.
kentsimmons.uwinnipeg.ca /cm1504/membranefunction.htm   (563 words)

 CiteULike: A mutant plasma membrane ATPase, Pma1-10, is defective in stability at the yeast cell surface.   (Site not responding. Last check: )
CiteULike: A mutant plasma membrane ATPase, Pma1-10, is defective in stability at the yeast cell surface.
A mutant plasma membrane ATPase, Pma1-10, is defective in stability at the yeast cell surface.
Pma1 is a plasma membrane H(+)-ATPase whose activity at the cell surface is essential for cell viability.
www.citeulike.org /user/adiel/article/180114   (217 words)

 Cell Membrane   (Site not responding. Last check: )
The cell membrane is made up of three parts, phosholipids which are magenta and green, the proteins which are orange and red, and the carbohydrates which are fl.
It is not unusual for carbohydrates, or sugars, to attach to the cell membrane phospolipids and proteins.
The cell membrane regulate's the exchange of vital substances between the content of the cells and it external enviroment.
sun.menloschool.org /~cweaver/cells/e/cell_membrane   (329 words)

 CiteULike: Ergosterol is required for targeting of tryptophan permease to the yeast plasma membrane.   (Site not responding. Last check: )
In wild-type cells, the plasma membrane localization of Tat2p is regulated by the external tryptophan concentration.
Tat2p is transported from the Golgi apparatus to the vacuole at high tryptophan, and to the plasma membrane at low tryptophan.
The plasma membrane targeting of Tat2p is dependent on detergent-insoluble membrane domains, suggesting that sterol affects the sorting through the organization of lipid rafts.
www.citeulike.org /user/adiel/article/179819   (454 words)

 The Cell Membrane
To perform the function of the organelle, the membrane is specialized in that it contains specific proteins and lipid components that enable it to perform its unique roles for that cell or organelle.
In essence membranes are essential for the integrity and function of the cell.
Membranes help organize the cell into domains and microdomains.
cellbio.utmb.edu /cellbio/membrane.htm   (412 words)

 Plasma Membrane   (Site not responding. Last check: )
The cytoplasm of cells is bounded by a membrane referred to as the cell membrane or plasma membrane.
The fluid-mosaic model for the structure of the cell membrane holds that the membrane consists of a protein-embedded bilayer of phospholipids, where the lipids' hydrophobic tails are pointed toward the center of the membrane and their hydrophilic heads toward the surfaces of the membrane.
With regard to molecules, the cell membrane is very permeable to water, certain lipid-soluble substances, amino acids, and sugars, but relatively impermeable to large molecules such as proteins and polysaccharides.
www.scientia.org /cadonline/Biology/eukaryotic/plasmembrane.ASP   (615 words)

 Plasma Membrane
As mentioned previously the plasma membrane is composed of a bilayer.
The plasma membrane is assymetric with respect to the lipid distribution.
Proteins in the plasma membrane serve as transporter molecules, i.e.
www.prism.gatech.edu /~gh19/b1510/memtra.htm   (2182 words)

 Plasma Membrane
The cell membrane is the fist point the cell come into contact with the out side world, and thus is responsible for much of its relationship with the outside world.
Fluid refers to the membranes constantly changing or fluctuating shape, where mosaic refers to the diversity of proteins scattered through out the membrane.
The cell membrane or plasma membrane is made up of a lipid bilayer, proteins, carbohydrates, and several structures attached to the surface and scattered within the lipid bilayer (varies depending on the type of the cell).
web.mala.bc.ca /bio200/membrane.html   (403 words)

 Retention of prominin in microvilli reveals distinct cholesterol-based lipid micro-domains in the apical plasma ...
Membrane cholesterol−sphingolipid 'rafts', which are characterized by their insolubility in the non-ionic detergent Triton X-100 in the cold, have been implicated in the sorting of certain membrane proteins, such as placental alkaline phosphatase (PLAP), to the apical plasma membrane domain of epithelial cells.
At the cell surface, prominin remains insoluble in Lubrol WX and is selectively associated with microvilli, being largely segregated from the membrane subdomains containing PLAP.
We propose the coexistence within a membrane domain, such as the apical plasma membrane, of different cholesterol-based lipid rafts, which underlie the generation and maintenance of membrane subdomains.
www.nature.com /doifinder/10.1038%2F35023524   (243 words)

 Mechanisms for Transport Across Membranes   (Site not responding. Last check: )
The plasma membrane functions to isolate the inside of the cell from its environment, but it is imperative that such isolation not be complete.
The plasma membrane functions as a selectively permiable membrane with exquisite selectivity regarding which molecules cross and which direction they are allowed to travel.
A molecule or ion that crosses the membrane by moving down a concentration or electrochemical gradient and without expenditure of metabolic energy is said to be transported passively.
arbl.cvmbs.colostate.edu /hbooks/cmb/cells/pmemb/transport.html   (329 words)

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