Carbohydrates: Bountiful Sources of Energy and Nutrients
Carbohydrates contain carbon, hydrogen, and oxygen. Plants make the
carbohydrate glucose during photosynthesis.
Simple sugars include monosaccharides and disaccharides. The three
primary monosaccharides are glucose, fructose, and galactose.
Two monosaccharides joined together are called disaccharides. Glucose and
fructose join to make sucrose, glucose and glucose join to make maltose, and
glucose and galactose join to make lactose.
Starches are polysaccharides, and they are the storage form of glucose in
Glycogen is the storage form of glucose in humans. Glycogen is stored in the
liver and muscles. Liver glycogen provides glucose to help us maintain blood
glucose levels, while muscle glycogen is used for energy during exercise.
Dietary fibre is the indigestible part of plants, while functional fibre is the
indigestible forms of carbohydrate extracted from plants or manufactured in
the laboratory. Fibre may reduce the risk of many diseases and digestive
Carbohydrate digestion starts in the mouth, where chewing and an enzyme
called salivary amylase start breaking down the carbohydrates in food.
Digestion continues in the small intestine. Specific enzymes are secreted to
break starches into smaller monosaccharides and disaccharides. As
disaccharides pass through the intestinal calls, they are digested into
Glucose and other monosaccharides are absorbed into the bloodstream and
travel to the liver, where fructose and galactose are converted to glucose.
Glucose is transported in the bloodstream to the cells, where it is either used
for energy or stored in the liver or muscle as glycogen.
Insulin and glucagon are hormones secreted by the pancreas in response to
changes in blood glucose.
Insulin is secreted when blood glucose increases sufficiently, and it assists
with the transport of glucose into cells.
Glucagon is secreted when blood glucose levels are low, and it assists with
the conversion of glycogen to glucose and with gluconeogenesis.
The glycemic index is a value that indicates how much a food increases blood
glucose levels. High glycemic foods can trigger detrimental increases in blood
glucose for people with diabetes. The usefulness of the glycemic index for
making dietary recommendations is controversial.
The glycemic load is a value that indicates the effects on blood glucose that
result from the quality and quantity of carbohydrate consumed.
All cells can use glucose for energy. The red