UNIT –II
CARBOHYDRATES
These are composed of carbon,hydrogen,and oxygen .
Carbohydrates are the third main component of diet.
Carbohydrates are also expressed as “CHO” and are major source of energy in the diet.
Types :
v MONOSACCARIDES
v DISACCHARIDES
v COMPLEX
POLYSACCHARIDES .
MONOSACCHARIDES :-
This are also called
as simple sugars.
e.g :
v
Glucose
v
Galactose
DISACCHARIDES :
These are also called
as compound sugar .
e.g
v
Lactose
v
Maltose .
POLYSACCHARIDES :
They are more than
two sugars.
e.g
v
Hemicelluloses
v
Complex polysaccharides : usually consisting of
hundreds or thousands of monosaccharides.
Function :-
v
They provide energy for various physiological
process.
v
They spare the proteins
v
They make diet tasty and palatable
v
They are necessary for oxidation of fats.
v
They assimilate in various tissues where they
can be utilized by the body whenever necessary.
Sources :-
1.
STARCH :
these
are the main of human diet which are found in
v
Fruits
v
Sweet potato
v
Cereals
v
Rice
v
Roots
v
Wheat
v
Potato
v
Oil seeds.
2.
SUGAR :
Sugar along with starch is the main source
of energy. Its source are
Monosaccharides and disaccharides .
3.
CELLULOSE :-
This is indigestible part of diet. It helps
in defaection and removes constipation. It is found in vegetables and fruits.
These indigestible component of carbohydrate
with scarcely any nutritive value contributes to dietary fibre.
Fibers :-
Fibers or roughage consists of cellulose .
this part of carbohydrates are not digested by the digestive juices. They are
left unchanged after digestion.
Function of fibers:
v
The fiber absorbs water and this increases the
bulk of the stool and helps to reduce the tendency to constipation by
encouraging bowel movements.
v
The cholesterol lowering effect of types of
dietary fibre appears firmly established.
Carbohydrate
metabolism :
When a person take
food into his mouth the food is swallowed with saliva. In the saliva an enzyme
called “ptylin”, is present ptylin acts on cooked starches and simple sugars
converts into maltose. The action of ptylin continues in the stomach for about
20 minutes. Then food is passed through pyloric opening into the alkaline juice
of the duodenum pancrease, bile,amylase.
Amylase is an enzyme
present in the pancreatic juice. As the food comes into the last part of the
small intestine enzymes act on carbohydrates completing the digestion of
starches by converting disaccharides into monosaccharides.
Sl.no
|
Enzyme
|
Disaccharides
|
Monosaccharides
|
1
2
3
|
Sucrase
Lactase
Maltose
|
Sucrose
Lactose
Maltose
|
Glucose+ fructose
Glucose +galactose
Glucose
|
Absorption and storage :-
Absorption of
digested food takes place entirely in the small intestine. The simple sugar is
absorbed by the villi of the small intestine passes into the blood. Capillaries
are carried by the portal vein into the liver where excess sugar is stored as
glycogen. The use of glucose is to serve as the main body fuel for the
production of energy for work and heat.
The glucose required
for immediate carried straight through the liver into the hepatic veins and
inferior venecava and enters the circulation. Any excess not required for the
body’s immediate needs is converted by the liver cells or into glycogen which
is insoluble and is stored in the liver until required for use when sugar
needed by the body the glycogen is converted back into glucose and it passes
into the blood stream.
Daily requirement :-
Balanced diet should
derive 40% of energy from carbohydrates and their quantity depends on the
economic status of individuals.
Deficiency of carbohydrates :-
·
Hypoglycemia
·
Fatigue and decreased energy
·
Muscle wasting
·
Un healthy weight loss
·
Dehydration
·
Weakened immune system
·
Constipation
·
Mood swing.
Over consumption of
carbohydrates :
·
Dental carries
·
Obesity
·
Type 2 diabetes .
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