2. CARBOHYDRATES
Introduction:
carbohydrate is a biological molecule consisting of
carbon (C), hydrogen (H) and oxygen (O) atoms.
Previously they were referred as hydrates of carbon with
presence of hydrogen and oxygen in same ratio as in
water i.e., 2:1.
Therefore it could be represented by general formula
Cx(H2O)x
3. CARBOHYDRATES
Later it was found that some of them like deoxyribose
(C5H10O4) and rhamnose (C6H12O5) do not satisfy the
required ratio of H and O.
Presently, certain carbohydrates possess nitrogen
(glucose amine, C6H13O5N), phosphorus and sulphur and
don not fit in the above general formula.
4. CARBOHYDRATES
Moreover, formaldehyde (CH2O ), acetic acid (C2H4O2)
and lactic acid (C3H6O3) have C, H and O and also
satisfy the ratio of H and O as in water, but are not a
carbohydrates.
So the term carbohydrate is used for convenience rather
than for exactness.
Carbohydrates are now defined broadly to encompass a
wide variety of compounds.
5. CARBOHYDRATES
Carbohydrates are polyhyroxy aldehydes and ketones
and their derivatives or substance that yield one of these
compound on hydrolysis.
Substances derived from carbohydrates by reduction of
the carbonyl group (alditols), by oxidation of one or
more terminal groups to carboxylic acids, or by
replacement of one or more hydroxyl groups by a
hydrogen atom, an amino group, a thiol group, or similar
heteroatomic groups are all carbohydrates.
6. CARBOHYDRATES
Among the well-known carbohydrates are various
sugars, starches, and cellulose, all of which are important
for the maintenance of life in both plants and animals.
Carbohydrates are also called saccharides (sakcharon =
sugar or sweetness) for many of small molecular weight
with sweet taste not true for large molecules.
The word sugar which is often used for
‘monosaccharide’ may signify simple compounds
containing more than one monosaccharide unit.
7. CARBOHYDRATES
In early stage, carbohydrates are formed by plants from
carbon dioxide and water during photosynthesis.
Animals have no way of synthesizing carbohydrates
from carbon dioxide and rely on plants for their supply.
The carbohydrates are then converted into other organic
materials by a variety of biosynthetic pathways.
8. CARBOHYDRATES
Indispensable for organisms
Skeletal structure in plants, insects and crustaceans
Food reserve in the storage organs of plants and liver and
muscle in animals.
Important source of energy
9. CARBOHYDRATES
Occurrence of carbohydrates:
Terrestrial biomass constitutes a multifaceted collection
of low and high molecular mass products, exemplified
by sugars and amino acids, lipids, and biopolymers such
as cellulose, hemicelluloses, chitin, starch, lignin and
proteins.
By far the most abundant group of these organic
products and materials, are carbohydrates
10. CARBOHYDRATES
In fact it is about two thirds of the annually renewable
biomass.
Widely distributed in plant and animal tissues
Carbohydrate can be stored (starch and glycogen), also
form a major portion of the supporting tissue of plants
(cellulose) and of some animals (chitin in crustacea and
insects).
It Play a basic role as part of the nucleic acids DNA and
RNA.
11. CARBOHYDRATES
Other carbohydrates are components of a variety of
natural products, such as antibiotics, bacterial cell walls,
blood group substances, glycolipids, and glycoproteins.
Glycolipids and glycoproteins are involved in
carbohydrate-based recognition phenomena, which the
basis of glycobiology.
12. CARBOHYDRATES
Carbohydrates are found in a wide array of both healthy
and unhealthy foods—bread, beans, milk, popcorn,
potatoes, cookies, spaghetti, soft drinks, corn, and cherry
pie.
The most common and abundant forms are sugars, fibers,
and starches.
The healthiest sources of carbohydrates includes
unprocessed or minimally processed whole grains,
vegetables, fruits and beans.
13. CARBOHYDRATES
These sources promote good health by delivering vitamins,
minerals, fiber, and having important phytonutrients.
Unhealthier sources of carbohydrates include white bread,
pastries, sodas, and other highly processed or refined foods.
These items contain easily digested carbohydrates that may
contribute to weight gain, interfere with weight loss, and
promote diabetes and heart disease.
14. CARBOHYDRATES
Classification of carbohydrates:
Usually classified in three groups:
A. Monosaccharides: (mono-one, sakcharon-sugar).
The generic term ‘monosaccharide’ denotes a single
sugar unit without glycosidic connection to other such
units.
Sweet in taste.
15. CARBOHYDRATES
Often called simple sugars
Monosaccharides are compounds which possess free
aldehyde or ketone group and two or more hydroxyl
group.
They are simplest sugars and can not be hydrolyzed into
smaller units.
The general formula is Cn(H2O)n or CnH2nOn
The ending ‘ose’ is the suffix to denote a sugar
16. CARBOHYDRATES
B. Oligosaccharide or oligosaccharoses:
(oligo-few)
Compound sugars yielding 2 to 10 molecules of the same
or different monosaccharide on hydrolysis.
Oligosaccharide that yield two molecule of
monosaccharides on hydrolysis is called disaccharide.
17. CARBOHYDRATES
Similarly, oligosaccharide that yield three molecules of
monosaccharide are trisaccharide and son on.
The general formula of disaccharides is Cn(H2O)n-1 and
of trisaccharides is Cn(H2O)n-2 and so on.
Sucrose, maltose and lactose are examples of
disaccharide are sweet in taste
18. CARBOHYDRATES
Polysaccharides or polysaccharoses: (poly-many);
The compound sugars that yield more than 10 molecules
of monosaccharides on hydrolysis.
Their general formula is (C6H10O5)x
They may be further classified in two groups based upon
the types of monosaccharide produced on hydrolysis of
polysaccharides.
19. CARBOHYDRATES
Homopolysaccharides yield same type of
monosaccharides on hydrolysis.
Examples; starch, glycogen, cellulose, inulin, chitin.
Heteropolysaccharide yield different types of
monosaccharide on hydrolysis.
Examples; specific soluble sugar of pneumococcus type
II, Hyaluronic acid, pectin Chondroitin.
