CELL MEMBRANE - integral proteins, are thought to function...

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CELL MEMBRANE Cholesterol is another important component of cell membranes embedded in the hydrophobic areas of the inner (tail-tail) region. Most bacterial cell membranes do not contain cholesterol. Proteins are suspended in the inner layer, although the more hydrophilic areas of these proteins "stick out" into the cells interior as well as the outside of the cell. These integral proteins are sometimes known as gateway proteins. Proteins also function in cellular recognition, as binding sites for substances to be brought into the cell, through channels that will allow materials into the cell via a passive transport mechanism, and as gates that open and close to facilitate active transport of large molecules. The outer surface of the membrane will tend to be rich in glycolipids , which have their hydrophobic tails embedded in the hydrophobic region of the membrane and their heads exposed outside the cell. These, along with carbohydrates attached to the
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Unformatted text preview: integral proteins, are thought to function in the recognition of self. Multicellular organisms may have some mechanism to allow recognition of those cells that belong to the organism and those that are foreign. Many, but not all, animals have an immune system that serves this sentry function. When a cell does not display the chemical markers that say "Made in Mike", an immune system response may be triggered. This is the basis for immunity, allergies, and autoimmune diseases. Organ transplant recipients must have this response suppressed so the new organ will not be attacked by the immune system, which would cause rejection of the new organ. Allergies are in a sense an over reaction by the immune system. Autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythmatosis, happen when for an as yet unknown reason, the immune system begins to attack certain cells and tissues in the body....
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