Biological Membranes Essay Example for Free

Biological Membranes EssayInternal membranes for organelles Bilayer Permeability Low permeability to charged and polar substances Water is an exception small size, lack of charge, and its high intentness Shedding solvation shells for ions is very unlikelyCommon Features of Biological Membranes Sheet-like structure TWO-molecule thick (60-100A) Lipids, Proteins, and carbohydrates Lipids form the barrier. Proteins mediate distinct functions.Non-covalent assemblies (self-assembly, protein-lipid interaction) Asymmetric (always) Fluid structures 2-dimensional solution of oriented lipids and proteins Electrically polarized (inside negative -60mV) spontaneously forming in water Protein/lipid dimension = 1/4 4/1 Carbohydrate moieties are always outside the cell Protein/Lipid ratio Pure lipid insulation (neuronal cells) Other membranes on average 50% Energy transduction membranes (75%) Internal membranes of mitocondria and Each atom i at position ri, is hard-boiled as a point with a mass mi and a fixed charge qi. What is the Force Field? In molecular dynamics a molecule is described as a series of charged points (atoms) linked by springs (bonds). To describe the time evolution of bond lengths, bond angles and torsions, also the non-bonding vanguard der Waals and elecrostatic interactions between atoms, one uses a force field. The force field is a collection of equations and associated constants designed to reproduce molecular geometry and selected properties of tested structures. Energy Terms expound in the CHARMm Force Field