What Are The Major Components Of Biological Membranes And How Do They Contribute To Membrane Function?.

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as
conveyance of an action potential in neurones. However, despite the diversity of
function, the structure of membranes is remarkably similar.
All membranes are composed of lipid, protein and carbohydrate, but it is
the ratio of these components that varies. For example the protein component may
be as high as 80% in Erythrocytes, and as low as 18% in myelinated neurones.
Alternately, the lipid component may be as high as 80% in myelinated neurones,
and as low as 15% in skeletal muscle fibres.
The initial model for membrane structure was proposed by Danielli and
Davson in the late 1930s. They suggested that the plasma membrane consisted of a
lipid bilayer coated on both sides by protein. In 1960, Michael Robertson
proposed the Unit Membrane Hypothesis which suggests that all biological
membranes -regardless of location- have a similar basic structure. This has been
confirmed by research techniques. In the 1970s, Singer and Nicholson announced a
modified version of ...

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the distance between neighbouring
molecules, and this in turn increases the fluidity of the membrane. Other
important phospholipids include phospatidylserine and phosphatidylethanolamine,
the latter of which is found in bacteria.
The phosphate group of phospholipids acts as a polar head, but it is not
always the only polar group that can be present. Some plants contain
sulphonolipids in their membranes, and more commonly a carbohydrate may be
present to give a glycolipid. The main carbohydrate found in glycolipids is
galactose. Glycolipids tend to only be found on the outer face of the plasma
membrane where in animals they constitute about 5% of all lipid present. The
precise ...

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