Hydrophobic, or water-hating molecules, tend to be non- polar. A phospholipid molecule consists of a three-carbon glycerol backbone with two fatty acid molecules attached to carbons 1 and 2, and a phosphate-containing group attached to the third carbon. This arrangement gives the overall molecule an area described as its head the phosphate-containing group , which has a polar character or negative charge, and an area called the tail the fatty acids , which has no charge.
They interact with other non-polar molecules in chemical reactions, but generally do not interact with polar molecules. When placed in water, hydrophobic molecules tend to form a ball or cluster.
The hydrophilic regions of the phospholipids tend to form hydrogen bonds with water and other polar molecules on both the exterior and interior of the cell. Thus, the membrane surfaces that face the interior and exterior of the cell are hydrophilic.
In contrast, the middle of the cell membrane is hydrophobic and will not interact with water. Therefore, phospholipids form an excellent lipid bilayer cell membrane that separates fluid within the cell from the fluid outside of the cell. Phospholipid aggregation : In an aqueous solution, phospholipids tend to arrange themselves with their polar heads facing outward and their hydrophobic tails facing inward. The structure of a phospholipid molecule : This phospholipid molecule is composed of a hydrophilic head and two hydrophobic tails.
The hydrophilic head group consists of a phosphate-containing group attached to a glycerol molecule. The hydrophobic tails, each containing either a saturated or an unsaturated fatty acid, are long hydrocarbon chains. Proteins make up the second major component of plasma membranes. Integral proteins some specialized types are called integrins are, as their name suggests, integrated completely into the membrane structure, and their hydrophobic membrane-spanning regions interact with the hydrophobic region of the the phospholipid bilayer.
Single-pass integral membrane proteins usually have a hydrophobic transmembrane segment that consists of 20—25 amino acids. Some span only part of the membrane—associating with a single layer—while others stretch from one side of the membrane to the other, and are exposed on either side. Some complex proteins are composed of up to 12 segments of a single protein, which are extensively folded and embedded in the membrane.
This type of protein has a hydrophilic region or regions, and one or several mildly hydrophobic regions. This arrangement of regions of the protein tends to orient the protein alongside the phospholipids, with the hydrophobic region of the protein adjacent to the tails of the phospholipids and the hydrophilic region or regions of the protein protruding from the membrane and in contact with the cytosol or extracellular fluid. Structure of integral membrane proteins : Integral membrane proteins may have one or more alpha-helices that span the membrane examples 1 and 2 , or they may have beta-sheets that span the membrane example 3.
Carbohydrates are the third major component of plasma membranes. They are always found on the exterior surface of cells and are bound either to proteins forming glycoproteins or to lipids forming glycolipids. These carbohydrate chains may consist of 2—60 monosaccharide units and can be either straight or branched.
Along with peripheral proteins, carbohydrates form specialized sites on the cell surface that allow cells to recognize each other. Similar types of glycoproteins and glycolipids are found on the surfaces of viruses and may change frequently, preventing immune cells from recognizing and attacking them.
Cytochalasin D disruption of actin filaments in 3T3 cells produces an anti-apoptotic response by activating gelatinase A extracellularly and initiating intracellular survival signals. Acta , — Aimon, S. Membrane shape modulates transmembrane protein distribution.
Cell 28, — Amaro, M. Anderson, M. Aggregates of acetylcholine receptors are associated with plaques of a basal lamina heparan sulfate proteoglycan on the surface of skeletal muscle fibers. Cell Biol. Anderson, R. A role for lipid shells in targeting proteins to caveolae, rafts, and other lipid domains. Science , — Andrade, D. Cortical actin networks induce spatio-temporal confinement of phospholipids in the plasma membrane—a minimally invasive investigation by STED-FCS. Aoki, T. Antigenic structure of cell surfaces.
Bagatolli, L. Two-photon fluorescence microscopy observation of shape changes at the phase transition in phospholipid giant unilamellar vesicles. Balda, M. Tight junctions at a glance. Cell Sci. Bass, M. Syndecandependent Rac1 regulation determines directional migration in response to the extracellular matrix. Baumgart, T. Bernardino de la Serna, J. Cholesterol rules: direct observation of the coexistence of two fluid phases in native pulmonary surfactant membranes at physiological temperatures.
Berrier, A. Cell-matrix adhesion. Effect of sphingomyelin headgroup size on molecular properties and interactions with cholesterol. Botelho, R. Localized biphasic changes in phosphatidylinositol-4,5-bisphosphate at sites of phagocytosis. Bozic, B. Coupling between vesicle shape and lateral distribution of mobile membrane inclusions. E Stat. Soft Matter Phys. Brameshuber, M. Imaging of mobile long-lived nanoplatforms in the live cell plasma membrane. Buda, C. Structural order of membranes and composition of phospholipids in fish brain-cells during thermal acclimatization.
Callan-Jones, A. Curvature-driven lipid sorting in biomembranes. Cold Spring Harb. Canagarajah, B. Dynamics of cholesterol exchange in the oxysterol binding protein family. Cantor, R. Lipid composition and the lateral pressure profile in membranes. CrossRef Full Text. Capponi, S. Interleaflet mixing and coupling in liquid-disordered phospholipid bilayers.
Cebecauer, M. Lipid order and molecular assemblies in the plasma membrane of eukaryotic cells. Signalling complexes and clusters: functional advantages and methodological hurdles. Cerottini, J. Localization of mouse isoantigens on the cell surface as revealed by immunofluorescence. Immunology 13, — PubMed Abstract Google Scholar. Chazotte, B. The multicollisional, obstructed, long-range diffusional nature of mitochondrial electron transport.
Chen, Y. Lipid Res. Chiantia, S. Chum, T. The role of palmitoylation and transmembrane domain in sorting of transmembrane adaptor proteins. Collins, M. Tuning lipid mixtures to induce or suppress domain formation across leaflets of unsupported asymmetric bilayers. Contreras, F. Molecular recognition of a single sphingolipid species by a protein's transmembrane domain.
Nature , — Specificity of intramembrane protein-lipid interactions. Cortizo, A. Changes induced by glucose in the plasma membrane properties of pancreatic islets. Crawley, S. Shaping the intestinal brush border. Culbertson, C. Diffusion coefficient measurements in microfluidic devices. Talanta 56, — DePierre, J. Plasma membranes of mammalian cells: a review of methods for their characterization and isolation.
Devaux, P. How lipid flippases can modulate membrane structure. Digman, M. Detecting protein complexes in living cells from laser scanning confocal image sequences by the cross correlation raster image spectroscopy method. Di Rienzo, C. Fast spatiotemporal correlation spectroscopy to determine protein lateral diffusion laws in live cell membranes. Douglass, A. Single-molecule microscopy reveals plasma membrane microdomains created by protein-protein networks that exclude or trap signaling molecules in T cells.
Cell , — Dupuy, A. Protein area occupancy at the center of the red blood cell membrane. Duzgunes, N. Monolayer coupling in phosphatidylserine bilayers: distinct phase transitions induced by magnesium interacting with one or both monolayers. Edwards, S. Localization of G-protein-coupled receptors in health and disease. Trends Pharmacol. Eggeling, C. Super-resolution optical microscopy of lipid plasma membrane dynamics.
Essays Biochem. Direct observation of the nanoscale dynamics of membrane lipids in a living cell. Elowitz, M.
Protein mobility in the cytoplasm of Escherichia coli. Ernst, A. Determinants of specificity at the protein-lipid interface in membranes. FEBS Lett. Evans, E. Translational and rotational drag coefficients for a disk moving in a liquid membrane-associated with a rigid substrate.
Fluid Mech. Fantini, J. Three-dimensional architecture of extended synaptotagmin-mediated endoplasmic reticulum-plasma membrane contact sites.
Fraenkel, G. The physiological action of abnormally high temperatures on poikilothermic animals: temperature adaptation and the degree of saturation of the phosphatides. Frick, M. Modulation of lateral diffusion in the plasma membrane by protein density. Frisz, J. Sphingolipid domains in the plasma membranes of fibroblasts are not enriched with cholesterol. Frolov, V. Membrane curvature and fission by dynamin: mechanics, dynamics and partners.
Fujita, A. Gangliosides GM1 and GM3 in the living cell membrane form clusters susceptible to cholesterol depletion and chilling. Cell 18, — Fujiwara, T. Phospholipids undergo hop diffusion in compartmentalized cell membrane. Gaffield, M. Preferred sites of exocytosis and endocytosis colocalize during high- but not lower-frequency stimulation in mouse motor nerve terminals. Garcia-Parajo, M.
Nanoclustering as a dominant feature of plasma membrane organization. Golan, D. Lateral mobility of band 3 in the human erythrocyte membrane studied by fluorescence photobleaching recovery: evidence for control by cytoskeletal interactions. Golebiewska, U. Evidence for a fence that impedes the diffusion of phosphatidylinositol 4,5-bisphosphate out of the forming phagosomes of macrophages.
Cell 22, — Diffusion coefficient of fluorescent phosphatidylinositol 4,5-bisphosphate in the plasma membrane of cells. Cell 19, — Gowrishankar, K. Active remodeling of cortical actin regulates spatiotemporal organization of cell surface molecules. Grecco, H. Signaling from the living plasma membrane. Grossmann, G.
Membrane potential governs lateral segregation of plasma membrane proteins and lipids in yeast. EMBO J. Guigas, G. Effects of protein crowding on membrane systems. Gurtovenko, A. Lipid transmembrane asymmetry and intrinsic membrane potential: two sides of the same coin. Gut, J. Haberkant, P. Protein-sphingolipid interactions within cellular membranes. Hansen, C. Molecular mechanisms of clathrin-independent endocytosis. Hanson, M. A specific cholesterol binding site is established by the 2.
Structure 16, — Hartel, A. The molecular size of the extra-membrane domain influences the diffusion of the GPI-anchored VSG on the trypanosome plasma membrane. Hatzakis, N. How curved membranes recruit amphipathic helices and protein anchoring motifs.
He, H. Detecting nanodomains in living cell membrane by fluorescence correlation spectroscopy. Hebert, B. Herman, P. Depolarization affects the lateral microdomain structure of yeast plasma membrane. FEBS J. Hodgkin, A. A quantitative description of membrane current and its application to conduction and excitation in nerve. Honigmann, A. Hughes, B. The translational and rotational drag on a cylinder moving in a membrane.
Hung, M. Protein localization in disease and therapy. Hynes, R. The extracellular matrix: not just pretty fibrils. Ipsen, J. Phase equilibria in the phosphatidylcholine-cholesterol system. Ivankin, A. Cholesterol-phospholipid interactions: new insights from surface x-ray scattering data.
Jacobson, K. Lateral diffusion of proteins in membranes. Redistribution of a major cell surface glycoprotein during cell movement. Janetopoulos, C. Directional sensing during chemotaxis. Jaqaman, K. Cytoskeletal control of CD36 diffusion promotes its receptor and signaling function.
Jeon, J. The cell membrane enables non-polar molecules those that do not easily bind to water to pass from the region of high concentration to the region of lower concentration.
Transmembrane protein molecules called channel proteins interspersed in the membrane, assist molecules in navigating from the outer layer to the inner layer by generating diffusion-friendly gaps for molecules to pass through.
Osmosis is a type of passive transport that is identical to diffusion which involves a solvent passing through a selectively permeable or semi-permeable membrane from a higher concentration to a lower concentration.
Such solutions are made up of two parts that are a solvent and a solute. Active transport takes place against the normal concentration gradient across a semi-permeable membrane passing from the lower concentration region to the higher concentration region and involving energy intake from the ATP molecule. Transmembrane proteins are essential membrane-crossing proteins that can function as pathways for biological molecules.
It works on both the inner and outer membranes. The membrane is crossed several times by polytopic transmembrane proteins. Some proteins are from receptors, while some are from different channels. Passive transport is considered the transportation of ions that needs no energy, whereas active transport mechanisms need the energy to move molecules. Active transport is used regularly as ions are pumped against the concentration gradient by membrane proteins.
It is a class of integral proteins i. The membrane bilayer lipid molecules are mainly hydrophobic. The mechanisms through which cells transfer materials into or out of the cell that is too large to specifically pass through the lipid bilayer of the cell membrane are known as endocytosis and exocytosis. Any of the substances that are moved through exocytosis and endocytosis via the cell membrane are large molecules, microorganisms, and waste products.
Endocytosis is a mechanism by which cells take in substances from outside the cell by invading them in a vesicle. These may include substances like cell-supporting nutrients or bacteria that engulf and kill immune cells. Endocytosis tends to happen when a part of the cell membrane is folded by itself, encircling extracellular fluid and various substances or microbes.
The resulting vesicle breaks down and is transferred inside the cell. Phagocytosis and pinocytosis are two types of endocytosis. Phagocytosis , sometimes known as cell eating. It is the process by which cells rationalize massive fragments or cells, such as infected cells and bacteria. In both, plant and animal cells, pinocytosis is also known as cell drinking.
During pinocytosis, the cell removes substances from the extracellular fluid that it requires to function. They contain products like water and nutrients. Exocytosis is the process through which cells shift products from the interior of the cell to the extracellular fluid. When a vesicle fuses with the plasma membrane, exocytosis occurs causing the contents to be released outside the cell.
What makes up the cell or plasma membrane? The plasma membrane consists of a bilayer of phospholipids that are two back-to-back layers of phospholipids.
The phospholipid bilayer that forms a steady significant barrier within the two fluids is the essential structure. The components are inside and outside of the cell, according to the cell layer. Another basic element of the cell membrane is membrane proteins that are inserted within the lipid structure. One of the primary functions of membrane proteins is associated with transport. What are cell or plasma membranes made of? The major parts of the cell membrane are as follows:.
Phospholipids are an important aspect of the structure of the cell membrane. The membrane consists mainly of molecules called phospholipids, which are spontaneously arranged into a double layer of externally hydrophilic water-loving head and internally hydrophobic water-hating tails.
Such interactions with water are what allow the formation of plasma membranes. Hydrophobic molecules can quickly migrate through the plasma membrane if they are small enough because like the inside of the membrane, they dislike water. On the other hand, hydrophilic molecules do not pass through the plasma membrane without any support because they are water-loving.
Phospholipids possess both hydrophilic and hydrophobic functions. The hydrophilic regions — phospholipid heads — are often referred to as the water-loving regions. As a lipid bilayer, the phospholipid heads of the cell membrane are exposed to internal and external fluids.
The water-fearing regions are often referred to as hydrophobic regions. This component of the lipid structure consists of large, unsaturated, and non-polar portions. Undoubtedly, unsaturated fatty acids can interact with other non-polar particles. They do not readily react with water and polar molecules. Contact Us. The Galleries:. Photo Gallery. Silicon Zoo. Chip Shots. DNA Gallery. Amino Acids. Religion Collection.
Cocktail Collection. Screen Savers. Win Wallpaper. Mac Wallpaper.
0コメント