BIOCHEMISTRY OF
CARBOHYDRATES
Dr. Muhammad Shakil
MBBS, M.Phil, Ph.D
Associate Professor
Biochemistry
Biochemistry syllabus
• Cell, signal transduction, pH
• Chemistry of Carbohydrates
• Chemistry of Proteins
• Chemistry of Lipids
• Chemistry of Nucleic acids
• Enzymology
• Vitamins
• Minerals
• Nutrition
Carbohydrate
General characteristics
• The term carbohydrate is derived from the
french: hydrate de carbone (Hydrates of Carbon)
• compounds composed of C, H, and O
• empirical formula: (CH2O)n
Greek “sakcharon” = sugar
•Definition:
• Poly hydroxy aldehydes
• or poly hydroxy-ketones
•or substances which yield such substances on
hydrolysis are known as carbohydrates .
•Aldose – polyhydroxyaldehyde, eg
glucose
•Ketose – polyhydroxyketone, eg fructose
General biological functions
1. sources of energy
2. Absolutely required for RBCs’ & brain
cells.
3. Storage form of energy i.e. starch &
glycogen.
4. Intermediates in the biosynthesis of
other basic biochemical entities (fats
and proteins)
5. associated with other entities such as
glycosides, vitamins and antibiotics)
6.
Glyco protein & Glyco lipids are
components of cell membrane.
7.
form structural tissues in plants and in
microorganisms (cellulose, lignin,
murein)
8.
participate in biological transport, cellcell recognition, activation of growth
factors, modulation of the immune
system
9.
Used as drugs i.e. antibiotics & cardiac
Glycosides.
Biomedical importance
•Glucose is the sugar of the body
•Glucose is the precursor of other
sugars formed in the body e.g.
glycogen, ribose, galactose etc
•Ribose and deoxyribose sugars
forms part of the structural
frame works of DNA & RNA
Diseases associated with carbohydrate
metabolism are:
•Diabetes mellitus
•Lactose intolerance
•Glycogen storage diseases
•Galactosemia
•And many more
CLASSIFICATION
•Monosaccharides
•Disaccharides
•Oligosaccharides
•Polysaccharides
•Derived carbohydrates
MONOSACCHARIDES
•Simplest sugars, cant be hydrolyzed into
simpler molecules.
•Further classified as,
Aldoses
Ketoses
NAME
GENERAL
FORMULA
ALDOSES
KETOSES
(3 C)
C3H6O3
GLYCERALDEHYDE
DIHYDROXY-ACETONE
TETROSES (4 C)
C4H8O4
ERYTHROSE ERYTHROLUSE
PENTOSES (5 C)
C5H10O5
RIBOSE
RIBULOSE
HEXOSES (6 C)
C6H12O6
GLUCOSE
FRUCTOSE
HEPTOSES (7 C)
C7H14O7
SEDOHEPTOLUSE
NONOSES (9 C)
C9H18O9
NEURAMINIC ACID
TRIOSES
DISACCHARIDES
• Condensation products of 2 monosaccharide units
• carbohydrates that can be hydrolyzed into two
monosaccharide units
MALTOSE (D Glucose + D Glucose)
SUCROSE (D Glucose + D Fructose)
LACTOSE (D Glucose + D Galactose)
TREHALOSE, ISOMALTOSE
Oligosaccharides
•carbohydrates that can be hydrolyzed into a
few monosaccharide units. (From 3 to 10 units)
Condensation products of 3-10 mono saccharide
units, most of them are not digested by human
enzymes.
α DEXTRINS
MALTO TRIOSE (3 GLUCOSE RESIDUES)
POLY SACCHARIDES
•Condensation products
of > 10 mono saccharide units.
1.
HOMO POLY SACCHARIDES
2.
HETRO POLY SACCHARIDES
HOMO POLYSACCHARIDES
Have only one type of mono saccharide units.
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•
•
•
•
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STARCH
GLYCOGEN
CELLULOSE
DEXTRIN
DEXTRAN
INULIN
CHITIN
HETRO POLYSACCHARIDES
❖
Hemicellulose
❖
MUCO POLY SACCHARIDES
Also known as Glycosaminoglycan.
• Hyaluronic Acid,Chondriotin sulfate, Heparin sulfate,
Keratin sulfate, Dermatin sulfate, Blood group
substances.
❖
•
•
•
GLYCO CONGUGATES
Proteo glycans
Glyco lipids
Glyco proteins
DERIVED CARBOHYDRATES.
• Compounds which are derived from other
carbohydrates
• Reduction products i.e. Polyols (glycerol)
• Oxidation products i.e. sugar acids
• Deoxy sugars i.e. present in DNA
• Amino sugars
Monosaccharides
•The most important monosaccharides
are:
• Pentoses
• Hexoses
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Monosaccharides
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Glucose
• An aldohexose, is the most important of the
monosaccharides.
SOURCES
• Fruit juices, Cane / Beetroot, maltose,
Lactose, Hydrolysis of Starch.
• found in the free state in plant and animal
tissue.
• also known as dextrose and grape sugar.
Glucose cont
• Component of the disaccharides sucrose,
maltose, and lactose
• monomer of polysaccharides amylose,
amylopectin, cellulose, and glycogen.
• Glucose is the key sugar of the body and is
carried by the bloodstream to all body
parts.
• Fasting Blood Glucose level (70-110 mg /
dl )
Galactose
Galactose is an aldohexose
SOURCES
• Milk , seeds of Legumes.
• Galactose is synthesized in the mammary
glands to make the disaccharide lactose (milk
sugar).
• It is also a constituent of glycolipids and
glycoproteins in many cell membranes.
• Epimer of Glucose at C-4
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Fructose
• Fructose, a ketohexose, also known as
levulose (Levorotatory)
• Sources : Fruit juices, Honey, Cane /
Beetroot, Sucrose, Inulin
• is a constituent of the disaccharide
sucrose.
• Fructose is the major constituent of the
polysaccharide inulin.
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•Fructose is the sweetest of all the
common sugars, being about twice as
sweet as glucose.
•This accounts for the sweetness of highfructose corn syrup and honey.
• Seminal fluid has Fructose as nutrient
for spermatozoa.
•Can occur in both Furanose & Pyranose
forms
Monosaccharides
The Fischer projections of D-glucose, D-galactose and D-fructose are shown here.
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D-MANNOSE
• SOURCES
• Hydrolysis of plant Gum Mannan ( not
present in free form) .
• Present in Glycoproteins&
polysaccharides.
• Gets converted into Glucose in human
body.
• C-2 epimer of Glucose.
Pentoses of physiological
importance
Pentoses
• D-Ribose and its derivative
D-2-deoxyribose are the
most important pentoses
because they are found in
the nucleic acids RNA and
DNA.
• The 2-deoxy in D-2deoxyribose means an
oxygen is omitted from the
D-ribose molecule at carbon
#2.
Monosaccharides
The Fischer projections of the pentoses D-ribose
and D-2-deoxyribose are shown here.
Pentoses
• Ribulose is a ketose
that is related to
ribose.
• It is a biological
intermediate used by
cells to make other
monosaccharides.
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DEOXY SUGARS
•L- Fucose
•Deoxy Glucose
•D- Ribose
•L- Arabinose
•D- xylose
THANKS