Physical Modeling of Lipid Membranes

For preparing next semester Biofisika blog and team launch many modules for student of college especially for jember university of student (Jurusan Fisika/ Prodi Biofisika) . including teaching department, agriculture, pharmachy, biology and many department or faculty that need this module>>

Mathematical models of deformable, fluid membranes have been available for many years and have been successfully compared with experimental results, both on artificial and biological membranes. At the most fundamental level these theories rely on the single basic principle underlying statistical mechanics:

that the probability of observing a given membrane deformation depends on the
energy change involved in making this deformation The higher the energy,
the less likely the deformation.
Statistical mechanics tells us that the probability pi of an event i is related to its energy Fi according to:

pi ~ exp [– Fi /kBTm ]

This probability compares the deformation energy Fi to some energy source in the system. This energy is written F to remind us that it is a free energy and therefore includes changes in entropy, as well as internal and chemical energies Reactions that reduce the entropy of the system are disfavored in the same way as are those that involve a spontaneous increase in the energy by, for example, disruptingchemical bonds. Strictly speaking, that equation only holds for (sub)systems that are at equilibrium but this can often be a reasonable approximation, for example for small patches of membrane that can move and relax quickly, even though it may be inappropriate for the cell as a whole. In passive systems, the only energy source comes from the thermal fluctuations of energy kBT, where kB is the Boltzmann constant and T is the temperatureBiological systems are called “active”, because chemical energy, coming from, for example, ATP hydrolysis, can be harnessed by specific enzymes (molecular motors) to perform mechanical work. The cell membrane is generally the site of many active processes, including cytoskeleton polymerization and ion pumping. One may adopt the approach that these active processes provide an effective “membrane” temperature Tm > T and it is this that appears in Equation above.