Insulin vs. Glucagon
Normally, blood glucose concentrations in human blood should range between
70-110 milligrams (mg/ml). Insulin and glucagon operate in an antagonistic
(opposing) manner. The result is a precise control of blood glucose levels within
this range.
The insulin pathway is activated when blood glucose levels are too high. High
blood glucose levels (e.g., occurring after the stomach has digested a food high
in sugar) stimulate beta cells in the pancreas to release insulin. Insulin causes
an increased uptake of glucose from the blood; promotes conversion of glucose
into triglycerides in the liver, fat and muscle cells; and increases the cellular rate
of glycolysis – breaking glucose into smaller components that can be used for
synthesis of other compounds.
The glucagon pathway is activated when blood glucose levels are too low. Low
blood glucose levels (e.g., due to exercise combined with not eating for several
hours) stimulate the alpha cells in the pancreas to produce glucagon. Glucagon
causes the liver to convert stored glycogen into glucose, then release the glucose
into the blood (a process called glycogenolysis). The two hormones, insulin and
glucagon, each regulate the other. A decrease in insulin (as well as low glucose
levels) stimulates the secretion of glucagon, while an increase in insulin (as well
as an increase in blood glucose) suppresses glucagon secretion. This results in
a continuous cycle, with insulin and glucagon constantly monitoring blood
glucose levels and regulating their secretion to maintain these levels as nearly
constant as possible.
The main function of insulin is removal of excess blood glucose. Because all
cells use glucose as an energy source and as a raw material for making other
organic compounds, all cells except brain cells are targets for insulin. Since the
function of glucagon is opposite that of insulin, it stimulates the addition of
glucose to the bloodstream. Thus, it targets cells with high concentrations of
energy stored as glycogen, including the liver and skeletal muscles. It also
stimulates glucose production from fats, so adipose tissue cells are another target
of glucagon.
Lactose intolerance
Lactose intolerance is a common digestive problem where the body is unable
to digest lactose, a type of sugar mainly found in milk and dairy products. The
body digests lactose by using an enzyme called lactase to break down lactose
into two simpler sugars called glucose and galactose, which can then be easily
absorbed into the bloodstream. Enzymes are proteins that cause chemical
reactions to occur.