Classification of Carbohydrates

Carbohydrates are classified on the basis of their behavior on

hydrolysis. They have been broadly divided into following three
groups.
(i) Monosaccharides: A carbohydrate that cannot be hydrolyzed further
to give simpler unit of polyhydroxy aldehyde or ketone is called a
monosaccharide. About 20 monosaccharides are known to occur in
nature. Some common examples are glucose, fructose, ribose, etc. (ii)
Oligosaccharides: Carbohydrates that yield two to ten monosaccharide
units, on hydrolysis, are called oligosaccharides. They are further
classified as disaccharides, trisaccharide’s, tetra saccharides, etc.,
depending upon the number of monosaccharides, they provide on
hydrolysis. Amongst these the most common are disaccharides.
The two monosaccharide units obtained on hydrolysis of a
disaccharide may be same or different. For example, one molecule of
sucrose on hydrolysis gives one molecule of glucose and one molecule
of fructose whereas maltose gives two molecules of only glucose.
(iii) Polysaccharides: Carbohydrates which yield a large number of
monosaccharide units on hydrolysis are called polysaccharides. Some
common examples are starch, cellulose, glycogen, gums, etc.
Polysaccharides are not sweet in taste, hence they are also called non-
sugars.
The carbohydrates may also be classified as either reducing or
nonreducing sugars. All those carbohydrates which reduce Fehling's
solution and Tollens' reagent are referred to as reducing sugars. All
monosaccharides whether aldose or ketose are reducing sugars.
Introduction
The carbohydrates may be defined as optically
active polyhydroxy aldehydes or ketones or the
compounds which produce such units on
hydrolysis.
Carbohydrates are primarily produced by
plants and form a very large group of naturally
occurring organic compounds. Some common
examples of carbohydrates are cane sugar,
glucose, starch, etc. Most of them have a
general formula, Ch(H2O)y, and were
considered as hydrates of carbon from where
the name carbohydrate was derived. For
example, the molecular formula of glucose
(C6H12O6) fits into this general formula,
C6(H2O)6. But all the compounds which fit
into this formula may not be classified as
carbohydrates. For example, acetic acid
(CH3COOH) fits into this general formula,
C2(H2O)2but is not a carbohydrate. Similarly,
rhamnose, C6H1205 is a carbohydrate but does
Preparation of Glucose
1. From sucrose (Cane sugar): If sucrose is boiled with
dilute HCI or H2SO4 in alcoholic solution, glucose and
fructose are obtained in equal amounts.

2.From starch: Commercially glucose is obtained by

hydrolysis of starch by boiling it with dilute H2SO4 at
393 K under pressure.
Structure of Glucose
Glucose is an aldohexose and is also known as dextrose. It is the monomer of
many of the larger carbohydrates, namely starch, cellulose. It is probably the
most abundant organic compound on earth. It was assigned the structure given
below on the basis of the following evidences:
1.Its molecular formula was found to be C6H1206
2.On prolonged heating with HI, it forms n-hexane, suggesting that all the six
carbon atoms are linked in a straight chain.

3. Glucose reacts with hydroxylamine to form an oxime and adds a molecule

of hydrogen cyanide to give cyanohydrin. These reactions confirm the
presence of a carbonyl group (>C = 0) in glucose.
Biological significance
The importance of carbohydrates to living things can
hardly be overemphasized. The energy stores of most
animals and plants are both carbohydrate and lipid in
nature; carbohydrates are generally available as an
immediate energy source, whereas lipids act as a long-
term energy resource and tend to be utilized at a slower
rate. Glucose, the prevalent uncombined, or free, sugar
circulating in the blood of higher animals, is essential to
cell function. The proper regulation of glucose
metabolism is of paramount importance to survival.
Mitochondrial matrix

The ability of ruminants, such as cattle, sheep, and goats,

to convert the polysaccharides present in grass and similar
feeds into protein provides a major source of protein for
humans. A number of medically important antibiotics,
such as streptomycin, are carbohydrate derivatives. The
cellulose in plants is used to manufacture paper, wood for
Role in the biosphere
The essential process in the biosphere, the portion of
Earth in which life can occur, that has permitted the
evolution of life as it now exists is the conversion by
green plants of carbon dioxide from the atmosphere
into carbohydrates, using light energy from the Sun.
This process, called photosynthesis, results in both the
release of oxygen gas into the atmosphere and the
transformation of light energy into the chemical
energy of carbohydrates. The energy stored by plants
during the formation of carbohydrates is used by
animals to carry out mechanical work and to perform
biosynthetic activities.
Role in human nutrition
The total caloric, or energy, requirement for an individual
depends on age, occupation, and other factors but generally
ranges between 2,000 and 4,000 calories per 24-hour period
(one calorie, as this term is used in nutrition, is the amount of
heat necessary to raise the temperature of 1,000 grams of water
from 15 to 16 °C [59 to 61 °F]; in other contexts, this amount of
heat is called the kilocalorie). Carbohydrate that can be used by
humans produces four calories per gram as opposed to nine
calories per gram of fat and four per gram of protein. In areas of
the world where nutrition is marginal, a high proportion
(approximately one to two pounds) of an individual's daily
energy requirement may be supplied by carbohydrate, with most
of the remainder coming from a variety of fat sources.
Although carbohydrates may compose as much as 80 percent of
the total caloric intake in the human diet, for a given diet, the
proportion of starch to total carbohydrate is quite variable,
depending upon the prevailing customs. In East Asia and in
areas of Africa, for example, where rice or tubers such as
manioc provide a major food source, starch may account for as
much as 80 percent of the total carbohydrate intake. In a typical
Western diet, 33 to 50 percent of the caloric intake is in the form
of carbohydrate. Approximately half (i.e., 17 to 25 percent) is
represented by starch; another third by table sugar (sucrose) and
milk sugar (lactose); and smaller percentages by
monosaccharides such as glucose and fructose, which are
common in fruits, honey, syrups, and certain vegetables such as
Role in plant and animal structure
Whereas starches and glycogen represent the major reserve
polysaccharides of living things, most of the carbohydrate
found in nature occurs as structural components in the cell
walls of plants. Carbohydrates in plant cell walls generally
consist of several distinct layers, one of which contains a
higher concentration of cellulose than the others. The
physical and chemical properties of cellulose are strikingly
different from those of the amylose component of starch.
In most plants, the cell wall is about 0.5 micrometer thick
and contains a mixture of cellulose, pentose-containing
polysaccharides (pentosans), and an inert (chemically
unreactive) plastic-like material called lignin. The amounts
of cellulose and pentosan may vary; most plants contain
between 40 and 60 percent cellulose, although higher
amounts are present in the cotton fiber.
Polysaccharides also function as major structural
components in animals. Chitin, which is similar to
cellulose, is found in insects and other arthropods. Other
complex polysaccharides predominate in the structural
tissues of higher animals.
ACKNOWLEDGEMENT
In the Accomplishment of this Project Successfully,
many people have best owned upon me their blessings
and the heart pledged support, this time I am utilizing
to thank all the people who have been concerned with
project.
Primarily I would thank God for being able to
complete this project with success. Then I would like
to thank my principal and Chemistry teacher
Miss. Saily ma’am, whose valuable guidance has been
the ones that helped me patch this project and make
it full proof success his suggestions and his
instructions has served as the major contributor
towards the completion of the project.
Then I would like to thank my parents and friends
who have helped me with their valuable suggestions
and guidance has been helpful in various phases of
the completion of the project.
THANK YOU
CONTENTS
1. Introduction
2 Classification of Carbohydrates
3. Preparation of Glucose
4. Structure of Glucose
5. Biological significance
6. Role in the biosphere
7. Role in human nutrition
8. Role in plant and animal structure
 Chemistry
Investigatory Project

Carbohydr
ate

Submitted By: -Mr. Aayush

Submitted To: -Saily Kalyankar
Ma’am