the phosphate portion of the phospholipids in a membrane can be found embedded in the membrane.
the phosphate portion of the phospholipids in a membrane can be found embedded in the membrane.
where can the phosphate portion of the phospholipids in a membrane be found?
embedded in the membrane
biological membranes are found in both prokaryotic and eukaryotic cells. they surround cells and organelles with a semi-permeable barrier that prevents free flow of substances. the membrane consists of a phospholipid bilayer structure and often embedded or otherwise associated proteins, along with cholesterol and glycolipids. the phospholipid bilayer is a two-layer structure mainly composed of phospholipids, which are amphiphilic molecules that have hydrophilic and hydrophobic regions. the hydrophilic region contains the polar head group. this region is exposed to aqueous substances located mainly in the exterior portion of the biomembrane. the hydrophilic region consists of the non-polar acyl chains or fatty acids groups facing the interior of the biomembrane. phospholipids consist of two non-polar hydrocarbon chains with ester or ether bonds to the phosphate group which is also linked by ester or ether bonds to the polar hydrophilic region. the phospholipid carries a negative charge due to the presence of the phosphate group. its overall polarity depends on the charges of the hydroxyl groups or alcohols such as choline, ethanolamine, inositol, serine, etc. attached to the phosphate group. there are six basic functions that are associated with biomembranes:
ethanol-induced non-lamellar phases in phospholipids
in this study there are several atomic-scale molecular dynamics simulations created to illustrate how ethanol affects biomembranes containing phospholipids. the phospholipid membrane systems are comparable to the model membranes above but it only consists of one phospholipid which is palmitoyl-oleoyl-phosphatidylcholine (popc) or palmitoyl-oleoyl-phosphatidylethanolamine (pope). the primary difference between the phosphatidlycholine (pc) and phosphatidylethanolamine (pe) is that the three methyl groups attached to the nitrogen atom for the pc structure is replaced by three hydrogen groups. the overall purpose of this study is similar to the study described above determining the effects of ethanol on biomembranes and how it is able to increase disorder in the membrane interior region forming non-lamellar phases in phospholipids. the experimental method and analytical technique is quite different. in the previous study, it emphasized the nnr technique using a set of host phospholipids, exchanging lipids, ethanol, and cholesterol to create model membranes. an aqueous solution containing 5% ethanol (v/v) was maintained but the concentration of cholesterol was varied to prove how this sterol compound can inhibit the effects of ethanol (inducing a liquid-disorder phase or non-lamellar phases) which is depicted in the different plots of the equilibrium constant (k) versus the mol% of cholesterol for each model membrane. in this study, phospholipid membrane is comparable to the model membrane which consists of popc, ethanol, water and in some cases the addition of monovalent ions (na, k, and cl) that are transported throughout the membrane in the presence of ethanol. the concentration of ethanol varies ranging from 2.5 to 30 mol% in an aqueous solution but there is no addition of any sterol compound. the atomic-scale molecular dynamics simulations are used to monitor the changes in the phospholipid membrane. all the simulations are carried out using gromacs simulation suite software along with other methods that are essential to perform the simulations. the temperature and pressure are controlled at 310k and 1bar. the simulations are measured at various time frames which include ficoseconds (fs), picoseconds (ps), and nanoseconds (ns). a typical simulation is composed of approximately 128 popc lipids and 8000 solvent molecules which include water and ethanol. in each simulation ethanol molecules, water molecules, head group regions, acyl chains, and the monovalent ions are all color-coded which aids in interpreting the results of the simulations. the concentrations of ethanol are 2.5, 5.0, 15.0 and 30 mol%. the amount of ethanol molecules depend on the concentration of ethanol present in the phospholipid membrane. force field parameters are measured for the popc lipids and monovalent ions (na, k, and cl), which are very important. a summary of the atomic-scale molecular dynamics simulations is then provided which contains important information as followed: 1) a system number that corresponds to a particular phospholipid simulation 2) the concentration of ethanol mol% used in a particular simulation 3) the concentration of ethanol (v/v%) used for the simulation 3) the ethanol/lipid ratio that is derived from the simulation 4) the area (nm2) of the phospholipid membrane which details the expansion of the membranes as the concentration of ethanol is increased 5) the thickness of the membrane which is based on the distance between the average positions of the phosphorus atoms on opposite sides of the phospholipid membrane and 6) the tilt of the head group of the popc lipid based on changes in the angle towards the interior region of the phospholipid membrane which was surprisingly not very significant.
ethanol-induced non-lamellar phases in phospholipids