2. CARBOHYDRATES
• CARBOHYDRATES ARE ALDEHYDE OR KETONE DERIVATIVES OF
POLYHYDRIC ALCOHOLS
• Classification
• Monosaccharide
• Oligosaccharides
• Polysaccharides
1. homopolysaccharides
2. heteropolysaccharides
3. Monosaccharides
• Monosaccharides are those sugars that cannot be hydrolyzed into
simpler carbohydrates
• aldoses or ketoses, depending upon whether they have an aldehyde
or ketone functional group.
• Aldehyde and ketone groups are called carbonyl groups
• Aldehyde group present at the end
• Ketone group is not present at the end but at some where else
5. Disaccharides
• Disaccharides are condensation products of two monosaccharide
units; examples are maltose and sucrose.
• Glucose + glucose_________maltose
• Glucose + galactose________lactose
• Glucose + fructose_________sucrose
• Joined through o-glucosidic linkage
6.
7. Oligosaccharides
• Oligosaccharides are condensation products of three to ten
monosaccharides. Most are not digested by human enzymes.
• On hydrolysis yield 2-10 monosaccharides
• Α dextrin 8 glucose units
• Maltotriose 3 glucose units
8. Polysaccharides
• Polysaccharides are condensation products of more than ten
monosaccharide units
• 100-1000 units of monosaccharides
• Stores of fuels e.g glycogen, starch
• Structural element of cell
10. Heteropolysaccharides
• This is very large group containing 2 or more type of monosaccharides
derivatives along with other molecules
1. Glycos-amino-glycans or mucopolysaccharides
• hyaluronic acid
• chondroitin sulfate
• heparin
2. Glycoconjugates
Proteoglycan
Glycoprotein
3. Mucilages agar, vegetable gum and pectin
12. Isomerism in monosaccharides
• The compounds that possess same chemical formula but differ in
physical (M.p, B.p and density and viscosity)and chemical properties
(flammability, corrosive, chemical Rx) called isomers.
with four asymmetric carbon atoms, can form 16 isomers.
• C6H12O6
• Glucose
• Fructose
• Galactose
• mannose
13. Stereoisomerism
• Two or more monosaccharides having same structural
formula but differ from each other in configuration
In other words differ from each other in arrangement
of atom in space
• Geometrical or cis and trans
• Optical isomers
14. Sugars Exhibit Various Forms of Isomerism
The more important types of isomerism found with glucose are as follows:
1. Enantiomers
d and l isomerism: The designation of a sugar isomer
as the d form or of its mirror image as the l form is determined by its spatial
relationship to the parent compound of the carbohydrates,
• The orientation of the —H and —OH groups around the carbon atom
adjacent to the terminal primary alcohol carbon (carbon 5 in glucose)
determines whether the sugar belongs to the d or l series.
• When the —OH group on this carbon is on the right the sugar is the d
isomer; when it is on the left, it is the l isomer.
• Most of the monosaccharides occurring in mammals are d sugars, and the
enzymes responsible for their metabolism are specific for this
configuration.
15.
16. optical isomer
• The presence of asymmetric carbon atoms also confers
optical activity on the compound. When a beam of plane
polarized light is passed through a solution of an optical
isomer, it rotates either to the right, dextrorotatory (+), or to
the left, levorotatory (–). The direction of rotation of
polarized light is independent of the stereochemistry of the
sugar, so it may be designated d(–), d(+), l(–), or l(+).
• For example,
• the naturally occurring form of fructose is the d(–) isomer. In
solution, glucose is dextrorotatory, and glucose solutions are
sometimes known as dextrose.
