3. General characteristics
• Most carbohydrates are found naturally in bound
form rather than as simple sugars
• Polysaccharides (starch, cellulose, inulin, gums)
• Glycoproteins and proteoglycans (hormones, blood group
substances, antibodies)
• Glycolipids (cerebrosides, gangliosides)
• Glycosides
• Mucopolysaccharides (hyaluronic acid)
• Nucleic acids
4. Functions
• Main sources of energy in the body. RBC and Brain
cells fully depends on carbohydrate
• It provides 4 kcal/g
• Storage form of energy (glycogen)
• Excess carbohydrate is converted to fat
• Form structural tissues in plants and in
microorganisms (cellulose, lignin, murein)
• Participate in biological transport,activation of growth
factors, modulation of the immune system
6. Classification of carbohydrates
• Monosaccharides (monoses or glycoses)
• Trioses, tetroses, pentoses, hexoses
• Oligosaccharides
• Di, tri, tetra, penta, up to 9 or 10
• Most important are the disaccharides
• Polysaccharides or glycans
• Homopolysaccharides
• Heteropolysaccharides
7. Monosaccharides: The Single
Sugars
• Monosaccharides – single sugar units
– Glucose
• Found in fruits, vegetables, honey
• “blood sugar” – used for energy
– Fructose
• Found in fruits, honey, corn syrup
• “fruit sugar”
– Galactose
• Found as part of lactose in milk
8. Classification
Classification based on:
1. No. of carbon atoms present in a sugar molecule.
2. Presence of an aldehyde or ketone group
Monosaccharides
Length of sugar Aldehyde/ketone
Trioses
Tetroses
Pentoses
Hexoses
Heptoses
Aldose Ketoses
14. Isomerism
Defn: Substances having the same molecular formula but a
different structural formula are called isomers and the
phenomenon as isomerism.
Isomers
Structural isomers
{Connectivity differences}
Stereoisomers
{differences in configuration}
Cis-Trans isomers Optical isomers
15. Isomers of monosacchraides
• D & L isomerism: Enantiomers
• Optical isomerism: d & l isomers / + & - forms
• Epimers
• Anomers
• Aldose-Ketose isomers
16. 1.Enantiomers - Glucose Is Chiral
and Shows D/L Isomerism –
Enantiomers are a special type of stereo isomers that are
mirror images of each other
18. 2.Optical isomerism: d & l isomers /
+ & - forms
Dextrorotatory (d) Levorotatory(l)
- rotate to right - rotate to left
- use + symbol - use - symbol
- d-isomers - l-isomers
19. 3.Epimers – two monosaccharides differs from each
other in their configuration around a single specific carbon.
Epimers differ at 1 carbon in the above structures.
GALACTOSE IS EPIMER OF GLUCOSE AT C4
MANNOSE IS EPIMER OF GLUCOSE AT C2
20. 4.Anomers
α and β cyclic forms of D-glucose are known as anomers
α and β cyclic forms differs each other in the
configuration only around c1(anomeric carbon) known
as anomer
21. Polysaccharides or glycans
• homoglycans (starch, cellulose, glycogen, inulin)
• heteroglycans (gums, mucopolysaccharides)
• characteristics:
• polymers (MW from 200,000)
• White and amorphous products (glassy)
• not sweet
• not reducing; do not give the typical aldose or ketose
reactions)
• form colloidal solutions or suspensions
22. Starch
• most common storage polysaccharide in
plants
• composed of 10 – 30% α−amylose and
70-90% amylopectin depending on the
source
• the chains are of varying length, having
molecular weights from several thousands
to half a million
23. Amylose and amylopectin are the 2 forms of starch. Amylopectin
is a highly branched structure, with branches occurring every 12
to 30 residues
25. Dextrins
• produced by the partial hydrolysis of
starch along with maltose and glucose
• dextrins are often referred to as either
amylodextrins, erythrodextrins or
achrodextrins
• used as mucilages (glues)
• also used in infant formulas (prevent the
curdling of milk in baby’s stomach)
26. Cellulose
• Polymer of β-D-glucose attached by β(1,4)
linkages
• Yields glucose upon complete hydrolysis
• Partial hydrolysis yields cellobiose
• Not digested by humans due to absence of
cellubiase
• Gives no color with iodine
• Plays an important role in nutrition
• Acts as dietary fibre
27. Glycogen
• also known as animal starch
• stored in muscle and liver
• present in cells as granules (high MW)
• contains both α(1,4) links and α(1,6) branches at
every 8 to 12 glucose unit
• complete hydrolysis yields glucose
• glycogen and iodine gives a red-violet color
• hydrolyzed by both α and β-amylases and by
glycogen phosphorylase
28. Inulin
∀ β-(1,2) linked fructofuranoses
• linear only; no branching
• lower molecular weight than starch
• colors yellow with iodine
• hydrolysis yields fructose
• sources include onions, garlic, dandelions and
jerusalem artichokes
• used as diagnostic agent for the evaluation of
glomerular filtration rate (renal function test)
Jerusalem artichokes
29. Chitin
• chitin is the second most abundant
carbohydrate polymer
• present in the cell wall of fungi and in
the exoskeletons of crustaceans,
insects and spiders
• chitin is used commercially in coatings
(extends the shelf life of fruits and
meats)
34. Hyaluronic acid derivatives
• Found in cartilage,tendons,bones,vitreous humor of eyes
• Repeating units of
• N acetyl glucosamine and glucuronic acid
• Acts as a shock absorbent
• Prevents the friction inbetween the bones
• several products are used in the management of osteoarthritis
symptoms
– Hyalagan and Synvisc
• others are used as ophthalmic surgical adjuncts in cataract
extractions, intraocular lens implantation, corneal transplant and
retinal attachment surgery (Healon, Amvisc, AMO Vitrax)
36. CHONDROITIN SULPHATE
• Present in connective tissue
• Seen in cartilages,bones,and tendons
• Repeating units of N acetyl galactosamine
and glucuronic acid
37. KERATAN SULPHATE
• Doesnot contain uronic acid
• Found in cornea,tendons,nails,hair
• Repeating units are galactose and N
acetyl glucosamine
38. DERMATAN SULPHATE
• Found in skin, blood vessels, and heart
halves
• Repeating units of N acetyl glucosamines
and iduronic acid
39. HEPARIN
• found in liver,lungs,spleen and monocytes
• Repeating units of glucosamine and
iduronic acid
• Act as a anticoagulant
• Prevents the intravascular coagulation
• Activates antithrombinIII which inturn
inactivates thrombin,factor X and factor IX
40. GLYCOPROTEINS
• Carbohydrates when attached to
polypeptide chain ,called glycoproteins
• Seen in almost all tissues and cell
membranes
• Composed of
• Glucose,mannose,galactose,N acetyl
glucosamine,N acetyl galactosamine,and
N acetyl neuraminic acid
