Carbohydrates are the main source of energy in
a common man's diet. Carbohydrates are made up of carbon, hydrogen
and oxygen (hence the name : carbo + hydrates). Each gram of carbohydrate
provides approximately 4 Calories in diet (except cellulose, which
doesn't give us any energy).
Carbohydrates are of the following types:
Starch is basic to human diet. It is the most important
of all carbohydrates. It is found in abundance in cereals, roots
and tubers. A good example of starch is potato. Chemically, starch
contains numerous sugar molecules joined together in chains and
Starch is stored in human body in the form of glycogen.
An average human contains about 500 grams of glycogen in his body.
Most of it is concentrated in liver and muscles. This reserve is
rapidly exhausted on fasting. It is estimated that all glycogen
is depleted from the body within 48 hours of fasting. Once the glycogen
reserve is depleted, the body starts breaking up protein and stored
fat for energy.
Sugars are usually sweet in taste. Some sugars
may have a bitter aftertaste too. Sugars can be monosaccharides
(like glucose, fructose and galactose) or disaccharides (sucrose,
lactose and maltose). These monosaccharide and disaccharide sugars
are highly soluble in water, and are therefore, easily assimilated.
Because they dissolve readily in water, sugar solutions have traditionally
been used as a quick source of energy.
Cellulose is largely indigestible in human beings.
Herbivores like cow, buffalo, gazelle etc. can obtain energy from
cellulose because they have enzymes that digest cellulose into smaller
sugars. But we humans lack the enzymes required to digest the cellulose.
Therefore, cellulose doesn't give us any energy. It forms dietary
fibers which are very important in the protection of health.
Cellulose is present abundantly in fresh fruits,
vegetables, salads, cereals, and almost any plant product for that
matter. Paper is made up of cellulose fibers. Wood contains cellulose
in abundance. Wheat husk abounds in cellulose. Now you have a fair
idea what ellulose is.