Plasma Membrane Structure Model

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In 1935, the first plasma membrane structure model was introduced by Danielli and Davson. They proposed that the membrane is made of phospholipid bilayer that consists of hydrophobic head and the hydrophilic tail. Hydrophilic head, which is polar, facing towards the water molecules and said to be coated with protein. Hydrophilic tail, which is non-polar is not facing water molecules and sandwiched between the two bilayers. At regular intervals of the surface of the plasma membrane, there are also pores which are 1 nm size. The structure is stable, static and rigid. This model is known as Danielli–Davson model. After that, in 1959, after the electron microscope has been discovered, Robertson studied the electron micrograph of the plasma membrane. …show more content…
Viscosity is depended on how densely the individual lipid molecules are packed together and this is affected by the composition of the lipid molecules that make up the membrane and the temperature of the surrounding. In high temperature, the membrane is said to be more fluid than in lower temperature. It is because, in high temperature, the phospholipid is further from each other because they have higher kinetic energy. Therefore, the further the phopholipid between each other, the fluidity the membrane is. Besides that, fatty acids of the lipid that composed of saturated hydrocarbon tend to have straight shape so it will pack more tightly. The double bonds in unsaturated fatty acids will make the lipid molecules are less straight and more loosely packed so that it will become more fluid while in saturated tend to have straight shape because each carbon is bound to the maximum number of hydrogen atoms. Membrane remains in a fluid state in wide range of temperature. In very low temperature, the lipid molecules become closely packed and the membrane forms a highly viscous semisolid gel. At any given temperature, the fluidity of a membrane is related to the degree to which the membrane lipids are unsaturated. The more unsaturated membrane is, the lower its geiling temperature, the more fluidity it …show more content…
It means that the proteins and other components that make up of one half of the lipid bilayer are different from the other half of the membrane. It is important because one of the half of the membrane has and carries different functions from the other half of the membrane. For example, one half of the external lipid bilayer is attached with glycolipid and carbohydrates and the other half is attached with cytoskeleton that binds on the internal membrane. Glycolipid and carbohydrates are important in cell-cell recognition whereas cytoskeleton is important in maintaining the cell shape. Besides that, there are also hormones and growth factors bind on its surface on the external membrane of the phospholipid

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