Describe
the role of proteins , glycolipids and cholesterol in the structure
of the cell
surface membrane .
Answer
The cell surface membrane is composed of a phospholipid
bilayer and along the membrane , there are numerous protein molecules , which
are arranged in a mosaic pattern . Due to the phospholipid bilayers , the
membrane is said to be selective or semi-permeable to certain substances .
Proteins that are found along the cell membrane also play a role in
transporting water-soluble ions across the membrane by the process of
facilitated diffusion . These proteins form channels by which ions are able
passes through the cell surface membrane . Other roles of the proteins in the
membrane are to give structural support for the cell surface membrane , to
allow calls to recognized by other agents ( e.g. enzymes , hormones and
antibodies ) and to assist in the active transport of materials across the
membrane .
Glycolipids are carbohydrate chains attached to the surface
of the membrane and generally perform two roles :
(1)
They allow cells to be recognized by other
calls and agents in the body , as well as receptor sites for chemical signals .
For example , the human ABO blood system is the result of different glycolipids
on the cell surface membrane of the red blood cells .
(2)
They
also serve to stabilize the membrane structure .
The role of cholesterol
is to act as a plug for reducing the entry and exit of polar molecules across
the cell surface membrane and make the membrane more stable . Cholesterol also
functions to make the cell surface membrane more flexible and fluid by
disturbing the packing of phospholipids to prevent rigidity .
Assignment submitted by L.E., Teh, E.L., Wong, Tan Findy 2011/2012 (IBM)
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