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Insulin:
Insulin, a polypeptide, is secreted from the pancreas
in response to a hyperglycemia condition which usually results
shortly after ingesting a meal. The structure is shown on the
left.
Insulin Protein - Chime
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The major effect of insulin is to promote the transport of
sugar across the cell membrane of fat and muscle cells. In addition,
insulin promotes anabolic processes such as increasing the rate
of synthesis for glycogen (glycogenesis),
fatty acids, and proteins. Insulin inhibits the catabolic processes
such as the breakdown of glycogen and fat.
A deficiency of insulin (hypoinsulinism) results in a permanent
hyperglycemic condition known as diabetes mellitus. If little
or no insulin is present, glucose cannot be utilized properly
by the cells and accumulates in the blood. Fatty acid metabolism
is also upset. For this reason, a detailed study of diabetes
mellitus must wait until the next chapter.
Hyperinsulinism (too much insulin) leads to the hypoglycemic
condition. Excessive amounts of glucose are removed from the
blood. Severe hypoglycemia may result when a diabetic injects
too much insulin. A severe insulin shock may result in a coma
since glucose does not reach the brain. A diabetic usually carries
a glucose rich food, such as candy, to provide a quick supply
of glucose to replenish depleted glucose levels caused by too
much insulin.
A functional type of hypoglycemia results in some individuals
from an over stimulation of insulin. The causes of hypoglycemia
are not completely understood, but it occurs in some people after
eating heavily sugared food such as heavily sugared cereal and/or
coffee and sweet rolls. The initial high glucose levels over
stimulates the pancreas to produce too much insulin. The excess
insulin causes blood sugar levels to drop below normal after
2-3 hours which may cause the person to feel sleepy, irritable,
and generally tired. The condition is only exacerbated by a "quick
fix" of more sweetened coffee, pastry, or candy since more
insulin is produced again. A protein rich breakfast would correct
the condition by allowing glucose to enter the blood stream more
slowly.
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