Carbohydrate 2nd lecture Biochemistry

1. Carbohydrate chemistryCarbohydrate chemistry
StreaksStreaks
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2. CarbohydratesCarbohydrates
 Carbohydrates are polyhydroxyCarbohydrates are polyhydroxy
aldehydes or ketons.aldehydes or ketons.
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3. Classification of carbohydratesClassification of carbohydrates
Carbohydrates are classified into:Carbohydrates are classified into:
– monosaccharides,monosaccharides,
– disaccharides,disaccharides,
– oligosaccharidesoligosaccharides
– polysaccharides.polysaccharides.
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4. SaccharidesSaccharides
Scientist use the word saccharides toScientist use the word saccharides to
describe sugarsdescribe sugars Greek “Greek “sakcharon”sakcharon” ==
sugarsugar..
If there is only one sugar molecule it isIf there is only one sugar molecule it is
known as aknown as a monosaccharidemonosaccharide
If there are two it is aIf there are two it is a disaccharidedisaccharide
When there are a whole bunch, it is aWhen there are a whole bunch, it is a
polysaccharidepolysaccharide..
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5. MonosaccharidesMonosaccharides
 The simplest form of carbohydratesThe simplest form of carbohydrates
 They are further classified according to:They are further classified according to:
 The number of carbon atoms in itsThe number of carbon atoms in its
backbonebackbone
 The functioning group (aldehyde orThe functioning group (aldehyde or
ketone)ketone)
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6. No. of
carbons
Name Aldehyde Ketone
3 Triose Glyceraldehyde Dihydroxy
acetone
4 Tetrose Erythrose Erythrulose
5 Pentose Ribose Ribulose
6 Hexose Glucose-
Galactose-
Mannose
Fructose
7 Heptose Sedoheptulose 66

7. Most of the names ofMost of the names of
carbohydrates end in -carbohydrates end in -oseose
GlucGlucoseose-What plants make-What plants make
MaltMaltoseose- used in making beer (disaccharide- used in making beer (disaccharide((
FructFructoseose – found in fruit (monosaccharide– found in fruit (monosaccharide((
SucrSucroseose- Table sugar (disaccharide- Table sugar (disaccharide((
LactLactoseose – In milk (disaccharide– In milk (disaccharide((
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8. Carbohydrates – polyhydroxyaldehydes or polyhydroxy-
ketones of formula (CH2O)n, or compounds that can be
hydrolyzed to them. (aka sugars or saccharides(
Monosaccharides – carbohydrates that cannot be
hydrolyzed to simpler carbohydrates; eg. Glucose or
fructose.
Disaccharides – carbohydrates that can be hydrolyzed
into two monosaccharide units; eg. Sucrose, which is
hydrolyzed into glucose and fructose.
Oligosaccharides – carbohydrates that can be
hydrolyzed into a few monosaccharide units.
Polysaccharides – carbohydrates that are are polymeric
sugars; eg Starch or cellulose.
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9. Aldose – polyhydroxyaldehyde, eg
glucose
Ketose – polyhydroxyketone, eg
fructose
Triose, tetrose, pentose, hexose, etc. –
carbohydrates that contain three, four,
five, six, etc. carbons per molecule
(usually five or six); eg. Aldohexose,
ketopentose, etc.
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10.  Of these; trioses, pentoses and hexoses are
most common in cells.
 If the carbon chain is long enough (five or more
carbons), the alcohol at one end of a
monosaccharide can attack the carbonyl group
(aldehyde or ketone) at the other end to form a
cyclic compound (hemiacetal or hemiketal
respectively).
 When aWhen a six-memberedsix-membered ring is formed, thering is formed, the
product of this reaction is called aproduct of this reaction is called a pyranosepyranose
 When aWhen a five-memberedfive-membered ring is formed, it isring is formed, it is
called acalled a furanosefuranose
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11.  The rings can open and re-close, allowing
rotation to occur around the carbonyl carbon
resulting in :
– Two distinct configurations (α and β
anomers) of the hemiacetals and hemiketals
are present.
 The anomeric carbon is the carbonyl carbon
(C1 of aldose or C2 of ketose).
 Carbohydrates can change spontaneously
between the α and β configurations-- a process
known as mutarotation.
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12. Pyranose ring
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B.B. AAnomerismnomerism
Sugars in solution exist in ring form and not in straight chainSugars in solution exist in ring form and not in straight chain
formform..
Aldosugar form mainlyAldosugar form mainly pyranosepyranose ring and ketosugar formring and ketosugar form
furanosefuranose ring structurering structure
CarbonCarbon 11, after ring formation becomes asymmetric and it is, after ring formation becomes asymmetric and it is
called as anomeric carbon atom. If the two sugars which differcalled as anomeric carbon atom. If the two sugars which differ
in the configuration at onlyin the configuration at only C1C1 in case of aldoses andin case of aldoses and C2C2 inin
ketoses are known as anomers and represented as alpha andketoses are known as anomers and represented as alpha and
beta sugarsbeta sugars..
E.g.E.g. αα-D glucose and-D glucose and ββ-D-glucose-D-glucose
αα-D fructose and-D fructose and ββ-D-fructose-D-fructose

14. 1414mirzaimran42@gmail.commirzaimran42@gmail.com

15. Furanose ring
+
D-fructose α - D-fructofuranose β -D-fructofuranose
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ISOMERISM IN CARBOHYDRATESISOMERISM IN CARBOHYDRATES
•The presence of asymmetric carbon atomsThe presence of asymmetric carbon atoms
(A carbon atom to which four different(A carbon atom to which four different
atoms or groups attached is known asatoms or groups attached is known as
asymmetric carbon) in a compoundasymmetric carbon) in a compound
produces following effectproduces following effect;;
•Sterioisomerism of the compoundSterioisomerism of the compound
•Confers optical activity to the compoundConfers optical activity to the compound..
11..SterioisomerismSterioisomerism
Compounds which are identical in compositionCompounds which are identical in composition
and structural formula but differ in spatialand structural formula but differ in spatial
configuration are called as sterioisomers.configuration are called as sterioisomers.
These includeThese include

17. IsomersIsomers
 These are compounds that have theThese are compounds that have the
same chemical formula e.g.same chemical formula e.g.
– glucose,glucose,
– fructose,fructose,
– mannose andmannose and
– galactosegalactose
– all have the chemical formulaall have the chemical formula
CC66 HH1212 OO66 ..
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EpimerismEpimerism::
The isomers formed due to variations in theThe isomers formed due to variations in the
configuration ofconfiguration of –H–H andand –OH–OH around a single chiralaround a single chiral
carbon atom in a sugar molecule is called ascarbon atom in a sugar molecule is called as
epimersepimers..
Mannose is 2 – epimer of glucose because these twoMannose is 2 – epimer of glucose because these two
have different configuration only around C2have different configuration only around C2..
Galactose is 4-epimer of glucose [at C4Galactose is 4-epimer of glucose [at C4[[

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2.Optical activity
The compounds having asymmetric carbon atoms
can rotate the beam of plane polarized light and
are said to be optically active.
An isomer which can rotate the plane of polarized
light to the right is called as dextrorotatory and
is designated as (d) or)+(
Example: D- (d)-glucose or it is also known as
dextrose.
While the isomer which rotates the plane of
polarized light to left is known as levorotatory,
and is identified as (l) or)-(.
Example: D-(l)-fructose.

20. EnantiomersEnantiomers
(sterioisomers(sterioisomers))
 These are special type of isomers in which the structure
is present in 2 pairs which are mirror images to each
other, resulting in D and L forms
 All carbohydrates contain at least oneAll carbohydrates contain at least one chiralchiral
(asymmetrical) carbon(asymmetrical) carbon and are, therefore can exist inand are, therefore can exist in
either of two conformations, as determined by theeither of two conformations, as determined by the
orientation of the hydroxyl group around the asymmetricorientation of the hydroxyl group around the asymmetric
carbon farthest from the carbonyl.carbon farthest from the carbonyl.
 The stereoisomer in which the -The stereoisomer in which the - OH extends to the rightOH extends to the right
is calledis called D-glyceraldehydeD-glyceraldehyde (from the Latin dexter=(from the Latin dexter=
right), and the stereoisomer in which the -right), and the stereoisomer in which the - OH extends toOH extends to
the leftthe left isis L-glyceraldehydeL-glyceraldehyde (from laevus = left).(from laevus = left).
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21. Enantiomers (sterioisomers)Enantiomers (sterioisomers)
D - and L - isomersD - and L - isomers
With a few exceptions, those carbohydrates that are of
physiological significance exist in the D-conformation
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23. Reactions involving monosaccharideReactions involving monosaccharide ss
Reducing sugars:
 The sugar is reducing if the oxygen
of the anomeric carbon (carbonyl
oxygen) is not attached to any other
structure.
 So glucose, galactose and fructose
are reducing sugars while sucrose is
not.
 Reducing sugars react with Benedict
reagent.
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24. Oxidation reduction reactionsOxidation reduction reactions
Oxidation of hydroxyl
group at C6 to carboxyl
group produces uronic
a.
• glucose gives
glucuronic acid,
• galactose gives
galacturonic acid..
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25.  Reduction of aldehyde or
keton group produces
alcohol
– glucose gives sorbitol,
– galactose gives galactilol,
– ribose gives ribitol
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26. Glycosidic bondsGlycosidic bonds
 It is the bond formed betweenIt is the bond formed between OHOH group ofgroup of
anomeric carbonanomeric carbon and aand a OHOH group orgroup or aminoamino groupgroup
of other compound calledof other compound called aglyconeaglycone
– If the group of aglycone is OH group, then it isIf the group of aglycone is OH group, then it is
O-glycoside bond (e.g. disaccharides).O-glycoside bond (e.g. disaccharides).
– If the group of aglycone is NH2­ group, then itIf the group of aglycone is NH2­ group, then it
is N-glycosideis N-glycoside..
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27. DisaccharidesDisaccharides
 The two monosaccharides are linked byThe two monosaccharides are linked by
a glycosidic bond to form disaccharidesa glycosidic bond to form disaccharides
 Physiologically important disaccharidesPhysiologically important disaccharides
are:are:
– sucrosesucrose
– lactoselactose
– maltose.maltose.
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28. Sucrose
•Found in sugar cane and sugar beets
•It is composed of glucose and fructose
linked by a-(1,2) -glycosidic bond
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29. LactoseLactose
 ItIt is found in the milk of mammalsis found in the milk of mammals
 It consists ofIt consists of galactosegalactose andand glucoseglucose in ain a
b-(1,4) glycosidic bond.b-(1,4) glycosidic bond.
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30. MaltoseMaltose

 The major degradation product of starchThe major degradation product of starch
 It is composed ofIt is composed of 2 glucose2 glucose monomersmonomers
in anin an αα-(1,4) glycosidic bond.-(1,4) glycosidic bond.
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31. PolysaccharidesPolysaccharides
 Most of the carbohydrates found in natureMost of the carbohydrates found in nature
occur in the formoccur in the form polysaccharides.polysaccharides.
 The main building blocks inThe main building blocks in
polysaccharides ispolysaccharides is D-glucose.D-glucose.
 When polysaccharides are composed of aWhen polysaccharides are composed of a
single monosaccharide, they are termedsingle monosaccharide, they are termed
homopolysaccharides.homopolysaccharides.
 Polysaccharides composed of more thanPolysaccharides composed of more than
one type of monosaccharide are termedone type of monosaccharide are termed
heteropolysaccharidesheteropolysaccharides .. 3131

32. OligosaccharidesOligosaccharides
Contain 3 - 10 molecules ofContain 3 - 10 molecules of
monosaccharide unitsmonosaccharide units..
eg: Maltotrioseeg: Maltotriose
(glucose+glucose+glucose(glucose+glucose+glucose((
PolysaccharidesPolysaccharides
Contain more than 10 molecules ofContain more than 10 molecules of
monosaccharide unitsmonosaccharide units
Classified intoClassified into homopolysaccharideshomopolysaccharides
andand heteropolysaccharidesheteropolysaccharides
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a)a) HomopolysaccharideHomopolysaccharide::
Polymer of same monosaccharide unitsPolymer of same monosaccharide units
ExamplesMonosaccharide UnitSources
StarchGlucosePlant, rice
DextrinGlucosefrom starch hydrolysis
GlycogenGlucoseliver, muscle
CelluloseGlucosePlant fibers
Inulin Fructosedahlia roots
ChitinN-acetyl glucosamineShells of arthropod

35. HydrolysisHydrolysis
Hydro=water lysis= break apartHydro=water lysis= break apart
Hydrolysis breaks down aHydrolysis breaks down a
disaccharide moleculedisaccharide molecule
into its originalinto its original
monosaccharidesmonosaccharides..
Hydrolysis, it means thatHydrolysis, it means that
water splits a compoundwater splits a compound..
When sucrose is added toWhen sucrose is added to
water, it splits apart intowater, it splits apart into
glucose and fructoseglucose and fructose..
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36. Do Too many carbohydrates makeDo Too many carbohydrates make
us fatus fat!!
If you eat more caloriesIf you eat more calories
than you expend inthan you expend in
energy, then anythingenergy, then anything
can be stored as fat -can be stored as fat -
protein, fat orprotein, fat or
carbohydratecarbohydrate..
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37. However if you do not take in anyHowever if you do not take in any
carbohydrates into your body youcarbohydrates into your body you
will use fat as fuelwill use fat as fuel..
Thank god for the low carb diet.
Now, nobody wants to eat me
because they think I make
them fat.
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38. What do we do with all the sugarWhat do we do with all the sugar??
Plants store glucose inPlants store glucose in
the form ofthe form of
polysaccharidespolysaccharides
known asknown as starchstarch inin
their rootstheir roots..
Animals store glucoseAnimals store glucose
in the from of ain the from of a
polysaccharide knownpolysaccharide known
asas glycogenglycogen in ourin our
liver and muscle cellsliver and muscle cells..
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39. CelluloseCellulose
The most abundant organicThe most abundant organic
molecule on earthmolecule on earth..
Gives trees and plantsGives trees and plants
structure and strengthstructure and strength..
Most animals can not breakMost animals can not break
the glucose linkage bythe glucose linkage by
normal means ofnormal means of
hydrolysis. Need specialhydrolysis. Need special
enzymesenzymes..
We need cellulose (fiber) toWe need cellulose (fiber) to
keep our digestive tractskeep our digestive tracts
clean and healthyclean and healthy..
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40. Polysaccharides are used in thePolysaccharides are used in the
shell of crustaceans like crabs andshell of crustaceans like crabs and
lobsters.lobsters.
ChitinChitin
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41. ChitinChitin: A nitrogenous derivative: A nitrogenous derivative
of of cellulosecellulose that is found in that is found in
abundance in the exoskeletonsabundance in the exoskeletons
of insects and crustaceans, asof insects and crustaceans, as
well as the cell walls of manywell as the cell walls of many
fungifungi..
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42. Carbohydrates also serve asCarbohydrates also serve as
structural elementsstructural elements..
The chains sticking out of the proteins inThe chains sticking out of the proteins in
the cell membrane are polysaccharidesthe cell membrane are polysaccharides
know as cell markersknow as cell markers..
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43. StarchStarch
 Starch is the major storage form ofStarch is the major storage form of
carbohydrate in plant cells.carbohydrate in plant cells.
 Unbranched starch is calledUnbranched starch is called amyloseamylose;;
branched starch is calledbranched starch is called amylopectinamylopectin
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44.  Amylose
- Is a glucose polymer with- Is a glucose polymer with a (1a (1--4)4) glycosidic bond.glycosidic bond.
- The end of the polysaccharide with an anomeric- The end of the polysaccharide with an anomeric
carbon (C1) that is not involved in a glycosidiccarbon (C1) that is not involved in a glycosidic
bond is called thebond is called the reducing endreducing end..
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45. Amylopectin:
- is a glucose polymer with mainly a(1-4) linkages,
- but it also has branches formed by a(1-6) linkages.
-The branches produce:
- a compact structure,
-and provide multiple chain ends at which enzymatic
cleavage of the polymer can occur.
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46. GlycogenGlycogen::
-- Glycogen is the major form of storedGlycogen is the major form of stored
carbohydrate in animals.carbohydrate in animals.
- It is a homopolymer of glucose linked by- It is a homopolymer of glucose linked by
a-(1,4) glycosidic linkagea-(1,4) glycosidic linkage
- it is also highly branched, with a-(1,6)- it is also highly branched, with a-(1,6)
branch linkages occurring every 8-10branch linkages occurring every 8-10
residuesresidues..
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47. CelluloseCellulose, a major constituent of plant cell walls, consists, a major constituent of plant cell walls, consists
of long linear chains of glucose, withof long linear chains of glucose, with b (1b (1--4)4) linkageslinkages..
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48. Lactose IntoleranceLactose Intolerance
more lactose is consumed than can bemore lactose is consumed than can be
digesteddigested
lactose molecules attract waterlactose molecules attract water
cause floating, abdominal discomfort, diarrheacause floating, abdominal discomfort, diarrhea
intestinal bacteria feed on undigested lactoseintestinal bacteria feed on undigested lactose
produce acid and gasproduce acid and gas
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49. Glucose HomeostasisGlucose Homeostasis
maintaining an even balance of glucose ismaintaining an even balance of glucose is
controlled by insulin and glucagoncontrolled by insulin and glucagon
insulininsulin
moves glucose into the bloodmoves glucose into the blood
glucagonglucagon
brings glucose out of storagebrings glucose out of storage
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50. Maintaining
Blood
Glucose
Homeostasis
Intestine
When a person eats,
blood glucose rises.
1
2
Insulin stimulates the uptake of
glucose into cells and storage
as glycogen in the liver and
muscles. Insulin also stimulates
the conversion of excess
glucose into fat for storage.
3
4
5
6
7 Blood glucose begins to
rise.
a
The stress hormone
epinephrine and other hormones
also bring glucose out of storage.
Glucose
Insulin
Glucagon
Glycogen
Glucagon stimulates liver
cells to break down glycogen
and release glucose into the
blood.a
Liver
Low blood glucose stimulates
the pancreas to release
glucagon into the bloodstream.
As the body's cells use
glucose, blood levels decline.
Glucagon
Pancreas
Fat cell
Liver
Muscl
e
High blood glucose stimulates
the pancreas to release insulin.
Pancreas
Insulin
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51. ImbalanceImbalance
diabetesdiabetes
after food intake, blood glucose rises and is notafter food intake, blood glucose rises and is not
regulated because insulin is inadequateregulated because insulin is inadequate
hypoglycemiahypoglycemia
blood glucose drops dramaticallyblood glucose drops dramatically
too much insulin, activity, inadequate food intake,too much insulin, activity, inadequate food intake,
illnessillness
diet adjustment includes fiber-rich carbs and proteindiet adjustment includes fiber-rich carbs and protein
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52. SugarSugar
½½comes from natural sources, ½ fromcomes from natural sources, ½ from
refined and addedrefined and added
sucrose, corn syrup, honeysucrose, corn syrup, honey
excess can lead to nutrient deficienciesexcess can lead to nutrient deficiencies
and tooth decayand tooth decay
empty caloriesempty calories
sugar and starch break down in the mouthsugar and starch break down in the mouth
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53. Starch and FiberStarch and Fiber
diet that includes starch, fiber and naturaldiet that includes starch, fiber and natural
sugarssugars
whole grains, vegetables, legumes, fruitswhole grains, vegetables, legumes, fruits
may protect against heart disease and strokemay protect against heart disease and stroke
reduces the risk of type 2 diabetesreduces the risk of type 2 diabetes
enhances the health of the large intestineenhances the health of the large intestine
can promote weight losscan promote weight loss
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54. Starch and FiberStarch and Fiber
starch intakestarch intake
45-65%45-65%
225225––325325grams (DV is 300 gramsgrams (DV is 300 grams((
900-1300900-1300kcal/2000 kcalkcal/2000 kcal
RDA is 130 gramsRDA is 130 grams
fiber intakefiber intake
Daily Value is 25 grams/2000 kcalDaily Value is 25 grams/2000 kcal
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57. Artificial SweetenersArtificial Sweeteners
help keep sugar and energy intake downhelp keep sugar and energy intake down
anything we eat has FDA approvalanything we eat has FDA approval
–saccharinsaccharin
–aspartameaspartame
–acesulfame potassiumacesulfame potassium
–sucralosesucralose
–neotameneotame
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58. Sugar ReplacersSugar Replacers
sugar alcoholssugar alcohols
provide bulk and sweetnessprovide bulk and sweetness
cookies, gum, candy, jellycookies, gum, candy, jelly
do contain minimal kcaldo contain minimal kcal
low glycemic responselow glycemic response
absorbed slowlyabsorbed slowly
do not cause dental cariesdo not cause dental caries
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