The document discusses carbohydrates and their role in the human body. It states that carbohydrates are the chief source of energy, providing 60-70% of the body's daily caloric needs. Carbohydrates are grouped into those that are utilized by the body (like glucose and glycogen) and those that are not (like cellulose). The document also outlines carbohydrates' role in fueling muscle work, synthesizing other compounds, and regulating blood glucose levels. It provides a table comparing the glycemic index of different foods.

2.  Dietary carbohydrates are the chief source
of energy.
 They contribute to 60-70% of total caloric
requirement of the body
 From the nutritional point of view,
carbohydrates are grouped into 2 categories.

3.  Carbohydrates utilized by the body starch,
glycogen, sucrose, lactose, glucose, fructose
etc.
 Carbohydrates not utilized (not digested)by
the body-cellulose, hemicellulose, pectin, gums
etc.

4.  Major sources of energy:
 Carbohydrates are the principal source of
energy, supplying 60-80% of the caloric
requirements of the body.
 Proteins paring action:
 Carbohydrates come to the rescue & spare
the proteins from being misused for caloric
purpose.

5.  Absolute requirement by brain:
 The brain & other parts of central nervous
system are dependent on glucose for energy.
 Required for the oxidation of fat:
 Acetyl CoA is formed in fatty acid oxidation.
 Acetyl CoA combines with oxaloacetate, the
latter is predominantly derived from
carbohydrate.

6.  Fats burns in a fuel of carbohydrate
 Excess utilization of fats coupled with
deficiency of carbohydrates leads to ketosis.
 Energy supply for muscle work:
 The muscle glycogen is broken down to lactic
acid (glycolysis) to provide energy for
muscle contraction.

7.  Synthesis of pentoses:
 Pentoses (e.g. ribose) are the constituents of
several compounds in the body e.g. nucleic
acids (DNA, RNA), coenzymes (NAD+, FAD).
 These pentoses are produced in
carbohydrate metabolism (HMP Shunt)

8.  Synthesis of non-essential amino acids:
 The intermediates of carbohydrate
metabolism, mainly the ketoacids (e.g.
pyruvic acid), serve as precursors for the
synthesis of non-essential amino acids.
 Synthesis of fat:
 Excess consumption of carbohydrates leads
to the formation of fat.

9.  Variations in increase & fall of blood glucose
levels after the ingestion of different
carbohydrate containing foods.
 These quantitative differences are assayed
by glycemic index which measures the time
course of postprandial glucose
concentrations from a graph.

10.  Glycemic index may be defined as the area
under the blood glucose curve after the
ingestion of a food compared with the area
under the blood glucose curve after taking the
same amount of carbohydrate as glucose.
 It is expressed as percentage.

11. Glycemic index =
Area under the blood glucose curve after
ingestion of test meal
______________________________________ x100
Area under the curve after ingestion of glucose

12.  The glycemic index of a complex carbohydrate
(i.e. starch) is lower than a refined
carbohydrate (i.e. glucose).
 This is explained on the basis of slow digestion
& absorption of complex carbohydrates.
 The glycemic index of carbohydrate is usually
lower when it is combined with protein, fat or
fiber.

13. Food item Glycemic index
Glucose 100
Carrots 90-95
Honey 80-90
Bread, rice 70-80
Banana, potato 60-70
Sweet potato 50-60
Apples 40-45
Ice cream, milk 35-40
Fructose 20-25
Soy beans 15-20

14.  Sources of carbohydrates:
 Carbohydrates are abundant in several
naturally occurring foods.
 These include table sugar (99%), cereals (60-
80%), pulses (50-60%), roots & tubers (20-40%) &
bread (50-60%).
 Requirement of carbohydrates:
 In a well balanced diet, at least 40% of the
caloric needs of the body should be met from
carbohydrates.

15.  Textbook of biochemistry - U Satyanarayana