3. INTRODUCTION
• Carbohydrate often termed as “sugars”.
• It is derived from Latin word hydrate de carbon means
“Hydrate of carbon”.
• Carbohydrate are biomolecules made up of carbon,
hydrogen, and oxygen.
• It is represented by a general formula Cn(H2O)n
• It is widely distributed in plants and animals.
• They are also known as ‘Saccharides’.
4. DEFINITION
“Carbohydrates are defined as polyhydroxy aldehydes
or polyhydroxy ketones and their derivatives”.
or
“Carbohydrates are also defined as polyhydroxy
alcohols that yield one of these compound on
hydrolysis”.
5. OCCURRENCE
• Carbohydrates are the basic components of food.
• They are sources of energy for all living beings.
• Autotrophs convert light energy into chemical energy
and synthesize carbohydrate during photosynthesis.
• They are widely present in grains, fruits, legumes,
cereals & vegetables.
• 1gm molecule of carbohydrate yields 4.9kcal energy.
7. MONOSACCHARIDES
• They are simple sugars.
• They do not hydrolyse.
• The general formula of monosaccharides is CnH2nOn
• These are colourless, crystalline, and sweet tasting
substances.
• They are rarely soluble in alcohol but soluble in
water.
• They have 3 to 7 carbon atoms per molecule.
• They are known as aldose (aldehyde group) and
ketose (ketone group).
8. • When the carbonyl is in position 1, forming an formyl
group (–CH=O), the sugar is called an aldose.
• If the carbonyl position is 2 or 3, the sugar is a
derivative of a ketone, and is called a ketose.
ALDOSE AND KETOSE
10. • A triose is a monosaccharide, or simple sugar,
containing three carbon atoms.
• Trioses are important in cellular respiration.
• During glycolysis, fructose-1,6-bisphosphate is
broken down into glyceraldehyde-3-phosphate and
dihydroxyacetone phosphate.
• Lactic acid and pyruvic acid are later derived from
these molecules.
• Ex. Glyceraldehyde, Dihydroxyacetone
1. TRIOSE (3C)
12. • Tetroses are monosaccharides with four carbon atoms.
• An aldotetrose has an aldehyde functional group at carbon
number one.
• The two common types of aldotetroses are D-Erythose and D-
Threose.
• One ketotetrose (D & L) is Erythrulose.
• The D configuration is more favor.
• They have two asymmetric carbons or chiral group and four
steroisomers.
• They are used in metabolic pathway and affect certain
enzyme activity in glycolytic pathway.
• Ex. Erythrose, Threose, Erythrulose
2. TETROSE (4C)
14. • Pentose is a monosaccharide (simple sugar) with five carbon
atoms.
• An aldopentose included Ribose and Deoxyribose occur in D
& L form.
• An ketopentose inclded D & L Ribulose.
• Aldopentose used in the synthesis of nucleotides and nucleic
acids.
• Pentoses exist in two forms, open-chain (linear) or closed-
chain (cyclic), that easily convert into each other in water
solutions.
• They are also called as Cyclic monosaccharides.
• They have high metabolic stability.
• Ex. Ribose, Ribulose, Deoxyribose
3. PENTOSE (5C)
17. • A hexose is a monosaccharides with six carbon atoms.
• Hexoses also exist in two forms, open-chain or cyclic, that
easily convert into each other in aqueus solutions.
• Hexoses are extremely important in biochemistry, both as
isolated molecules (such as glucose and fructose) and as
building blocks of other compounds such as starch, cellulose,
and glycosides.
• Its include aldohexose and ketohexose.
• The aldohexose that is D-glucose, which is the main "fuel" for
metabolism in many living organisms.
• Fructose is responsible for the sweet taste of many fruits, and
is a building block of sucrose, the common sugar.
• Ex. Glucose, Galactose, Mannose, Fructose.
4. HEXOSE (6C)
20. • A heptose is a monosaccharide with seven carbon atoms.
• They have either an aldehyde functional group in position
1 (aldoheptoses) or a ketone functional group in position 2
(ketoheptoses).
• They are intermediate compound of lipid biosynthesis.
• They are basically present in plants.
• EX. L-glycero-D-manno-heptose, Mannoheptose,
Sedoheptulose (calvin cycle), Mannoheptulose.
4. HEPTOSE (7C)
22. • Stereoisomers are isomers that have the same composition
but that differ in the orientation.
• Stereoisomers, a set of two molecules that are mirror image
of one another.
• The existence of these molecules are determined by concept
known as Chirality.
• A molecule is said to be chiral if its all valence is occupied by
different atom or group of atom.
• Two kinds of stereoisomers-
Enantiomers and Diastereomers.
STERIOISOMERS & CHIRALITY
24. • An enantiomer is one of two stereoisomers that are mirror
images of each other that are non-superposable (not
identical).
• In a pair of enantiomers, all of the chiral centers are of the
opposite configuration.
• There are two enantiomers of glucose, called D-glucose and
L-glucose.
• Both sterioisomers are inverted to each other.
• The D-enantiomer is the common sugar that our bodies use
for energy.
• It has n = 4 stereocenters or chiral group so therefore there
are 2n = 24 = 16 possible stereoisomers (including D-glucose
itself).
ENANTIOMER
25. DIASTEREOISOMERS
• Diastereomers (sometimes called diastereoisomers) are a
type of a stereoisomer.
• If two molecules are stereoisomers, but are not enantiomers,
are called diastereoisomers.
• In a pair of diastereomers, at least one or two chiral centers
are opposite to each other.
• By definition, two molecules that are diastereomers
are not mirror images of each other.
26. EPIMERS
• An epimer is one of a pair of diastereomers. The two epimers
(sugar) have opposite configuration at only one stereogenic
center out of at least two.
• They are not mirror image to each other. Epimers can be
enantiomers or diastereomers.
• When the molecule has only one stereocenter then
the epimers are enantiomers.
• When the molecule has two or more stereocenters then
the epimers are diastereomers.
• Glucose and mannose are C2 epimers, ribose and xylose are
C3 epimers, and gulose and galactose are also C3 epimers.
28. PROPERTY OF MONOSACCHARIDES
Physical property:
• Monosaccharides are colourless and crystalline
compounds.
• They are readily soluble in water.
• They have sweet in taste.
• The presence of asymmetric carbon atoms in a
compound give rise to the formation of isomers of that
compound.
• They have the property of mutarotation.
29. MUTAROTATION
• Mutarotation is the change in the optical rotation
because of the change in the equilibrium between two
anomers, when the corresponding stereocenters
interconvert. Cyclic sugars show mutarotation as α and
β anomeric forms interconvert.
• Mutarotation is occurs when the hydroxyl group at the
anomeric position (C-1) switches configuration between
alpha and beta.
• Glucose and fructose can undergo mutarotation.
30.
31. Chemical property:
• Monosaccharides show some special reactions due to the
presence of carbonyl and alcoholic group of the same
molecule.
• Both aldehyde or ketone group are involve in these reaction.
1. Oxidation: In the process of oxidation, the terminal
aldehyde group and keto group are oxidized.
a) Oxidation of aldehyde group (-CHO) results in the formation
of aldonic acid.
-CHO -COOH
Aldose Aldonic acid
33. b) Oxidation of terminal alcohol group in the formation of
uronic acid.
-CH2OH COOH
Alcohol group Uronic acid
Glucose Glucuronic acid
34. C) When aldose are oxidized by strong oxidizing agent (Nitric
acid), both –CHO group and –OH group are oxidized to form
dicarboxylic acid known as aldaric acid.
Aldose Aldaric acid
Glucose Glucaric acid
35. 2. Reduction: When monosaccharides are heated with
reducing agent, then the –CHO or –CO group is reduced
to alcohols.
–CHO - CH2OH
–CO CH2OH
Glucose Sorbitol
2H+
36. 3. Dehydration: When monosaccharides are heated with
conc. Sulphuric acid, they undergo dehydrate, means water
molecules are removed.
Hexose Hydroxymethyl furfural
Pentose Furfural
37. 4. Osazone formation: When sugars are boiled with phenyl
hydrazine, Osazone are produced. In this reaction only C1 &
C2 are involved. Osazones are highly coloured and crystalline
compounds and can be easily detected.
Glucose Glucosazone
38. 5. Ester formation: Esterification of carbohydrates are most
common reaction in carbohydrate metabolism.
Glucose Glucose 6- phosphate
39. FUNCTION OF MONOSACCHARIDES
• Cells use it as the primary source of energy and a metabolic
intermediate.
• The cells of the brain and the rest of the nervous system
depend exclusively on glucose for their energy.
• Glucose is one of the main products of photosynthesis and
fuels cellular respiration.
• Fructose is found in honey, tree and vine fruits, flowers,
berries and most root vegetables. It may be present as the
monosaccharide and/or as a component of sucrose.
• Pure, dry fructose is a very sweet, white, odorless, crystalline
solid and is the most water-soluble of all the sugars.
• Galactose rarely occurs as a monosaccharide in food as it is a
type of sugar that is less sweet than glucose.
40. • Galactose is found primarily in dairy products, sugar beets,
and other gums and mucilages. It is also synthesised by the
body, where it forms part of glycolipids and glycoproteins in
several tissues.
• Carbohydrates are a group of macromolecules that are a
vital energy source for the cell and provide structural
support to plant cells, fungi.
• Plants create cellulose to serve this function, while
some bacteria can produce a similar cell wall from slightly
different polysaccharides.
• Glucose is a product of photosynthesis, and plants obtain
energy from glucose through respiration. Humans acquire
glucose from food, and the body transforms this
monosaccharide into energy.
41. • The ribose and deoxyribose monosaccharides are vital
elements of RNA and DNA, which are the building blocks
of life.
• Derivatives of monosaccharides are found in nature. One
example of a monosaccharide derivative is vitamin C, also
called ascorbic acid, which is derived from glucose.
• Sugar substitutes, such as sorbitol and mannitol, are used as
sweeteners, and they form naturally in plants.
• Amino sugars, such as glucosamine, a derivative of glucose,
produce cartilage, connective tissue and chitin, a
component of an insect’s exoskeleton.
