How is a cell’s membrane structure suited to its functions?
Throughout the past century, scientists have been able to conduct more research on the structure of a cell membrane and understand its components and functions. The present agreed on model, created in 1972 by S. J. Singer and G. Nicolson, is called the fluid mosaic model. This model depicts that proteins (integral and peripheral) form a mosaic since they are floating in a fluid layer of phospholipids, which makes up the components of the cell membrane (along with cholesterol). Each of these parts of the membrane enables it to be more efficient. The purpose of a cell membrane is to support and protect the cell, but also to control the movement of materials in and out of it. It is selectively permeable1, creates a barrier between the cell and its environment and maintains homeostasis2. These functions are why the cell membrane is a vital cell structure. One of the most important parts of it is the phospholipid bilayer.
The phospholipid bilayer contains many phospholipids (diagram below) and is approximately five nanometers (1nm=1/1,000,000,000m) thick. Each phospholipid is composed of a non-polar (hydrophobic) region of two fatty acids pointing inwards and a polar (hydrophilic) phosphorylated alcohol head region pointing outwards on the exterior of the membrane. Connecting the phosphorylated alcohol and both fatty acids is a 3-carbon compound called glycerol. Since there is both a hydrophilic and a hydrophobic region of each phospholipid, then the phospholipids are always arranged in a bilayer. The bilayer has two main strengths: it’s fluidity and its selectively permeable structure. The layer tends to be fluid or flexible since the fatty acid areas do not attract each other very strongly. This is one of the strengths of the cell membrane since it allows animal cells to have a variable shape and also allows the process of endocytosis (allows macromolecules3 to enter the cell). This fluidity...
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