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carbohydrates
study carbohydrates
358
Medical
Undergraduate 1
11/26/2024

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Term
q
Definition
Term
ST
Definition
Term
CARBOHYDRATES =
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Biochemistry of Dietary
Definition
Term
Functional and Structural
Definition
Term
Carbohydrates I
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II
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By
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Asst. prof. Amira Abdel Hamid Kamel
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Medical Biochemistry Department
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Faculty of Medicine
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Term
Assiut University
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Term
Objectives
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Term
@ Identify different classes of carbohydrates
Definition
and list their
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biological importance.
Definition
Term
® Define chemistry and functions of monosaccharides
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and
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oligosaccharides and their derivatives
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Term
@ Define and classify polysaccharides.
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Term
@ Discuss structure and function medically important homo
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and hetero-polysaccharides.
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Term
o o
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is A Y .
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Definition of carbohydrates: Rat RSP
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Term
Carbohydrates are aldehyde (CHO) or ketone (C=O) derivatives of
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Term
polyhydric alcohols (have more than one OH group) or compounds
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Term
which yield these derivatives on hydrolysis.
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Term
Importance of carbohydrates:
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Term
The chief source of energy and form 60% of human diet.
Definition
Term
Important structural components in human cells
Definition
nucleic acids.
Term
Synthesis of antigens e.g. blood group substance.
Definition
Term
Forms a part of hormones
Definition
their receptors & immunoglobulins.
Term
fp eye
Definition
Term
. Hyalouronic acid (polysaccharide) is important for joint
Definition
Term
lubrication.
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Term
Classification of carbohydrates
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Term
According to the number of sugar units in the molecule there are
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Term
three types:
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Term
1.Monosaccharides (simple sugars): They contain one
Definition
Term
sugar unit
Definition
i.e., and the simplest form of sugars.
Term
2.Oligosaccharides: They contain 2 —10 monosaccharide
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Term
units per molecule.
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Term
3. Polysaccharides: They contain more than 10
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monosaccharide units per molecule.
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Term
NS
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Term
yor Al
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-Oligosaccharide t ‘
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I. Monosaccharides
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They are classified according to the number of carbon atoms into:
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Trioses: with three carbons
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Tetroses: with four carbons
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Pentoses: with five carbons
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Hexoses: with six carbons
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Each of these groups is subdivided according to the type of
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functional chemical group into:
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Aldoses (sugars containing aldehyde group)
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Ketoses (sugars containing ketone group).
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Medical significance of some Monosaccharides
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Term
® Ribose: is structural component in nucleic acids & free nucleotides.
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Term
® Glucose (grape sugar
Definition
blood sugar or dextrose). Other hexoses
Term
have to be converted into glucose to be utilized in the body. It
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appears in urine in diabetes mellitus.
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Term
@ Mannose: is a subunit in glycoproteins and sialic acid that enters in
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Term
the structure of gangliosides.
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Term
® Galactose: is the subunit of the milk sugar lactose. It enters in
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Term
structure of glycolipids and glycoproteins.
Definition
Term
® Fructose (semen sugar
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fruit sugar, levulose): It is the sweetest
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sugar known. It is the main sugar in bee’s honey.
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Term
Sugar derivatives of monosaccharides with
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Medical importance:
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1.Amino sugars or sugaramines (Replace hydroxyl
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Term
group at C2 by an amino group).
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Term
2.Deoxy sugars (Replace hydroxyl group at C2 or C3 or
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Term
C6 by hydrogen atom ).
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3. Sugar acids (product of oxidation of sugars).
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4. Sugar alcohols (product of reduction of sugars).
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1. Amino sugars (Sugaramines):
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- Replace OH group on C2 by an amino group.
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1. Glucosamine (Chitosamine): It enters in the structure of
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Term
some mucopolysaccharides. D
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Term
2. Galactosamine (Chondrosamine): It enters in the structure
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Term
of the sulfate-containing mucopolysaccharides.
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Term
3. Mannosamine: lt enters in the structure of antibiotics and
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Term
important for their activity e.g.
Definition
erythromycin.
Term
4. Sialic acid: It enters in structure of glycolipids and
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Term
Glycoproteins.
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Term
2. Deoxysugars:
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from L-Mannose).
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@od group substancek
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Wialic acid Deva)
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EEL is an amino sugar AAA)
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EE deoxy sugar since it contains two hydrogen AD
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@ sugar acid since it contains COOH group
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3. Sugar acids
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1. Gluconic acid used as Ca’ gluconate for intravenous
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supplementation of calcium.
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Term
2. L-ascorbic acid (vitamin C) is synthesized from glucose in plants
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Term
and animals except human
Definition
primates and guinea pig. It is an
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antioxidant.
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Term
3. Sialic acid ger
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Term
4
Definition
Glucuronic acid: It is synthesized in the liver and important in.
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1. Glucuronic acid enters in the structure of mucopolysaccharides
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Term
e.g. Hyalouronic acid.
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Term
2
Definition
Detoxication by conjugation of certain drugs and toxins and
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help excretion of bilirubin and steroid hormones.
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Term
3. L-iduronic acid is an isomer of D-glucuronic acid and it enters in
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structure of mucopolysaccharides e.g. Heparin
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Term
4. Sugar alcohols dh
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Term
>]
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1-Glyceraldehyde reduction gives glycerol that enters in structure of
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lipids
Definition
creams and explosives. ST > 7
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2- Ribose reduction gives Ribitol that is a part of the structure of
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vitamin B
Definition
(Riboflavin).
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3- Glucose reduction gives sorbitol that enters in medical industries. It
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Term
can not diffuse out of cells and its accumulates in cells
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causes osmotic
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damage to cells as in cataracts and neuropathy.
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4- Mannose reduction gives Mamnitol which is injected intravenously
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to reduce intracranial hypertension.
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O
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Sorbitol
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Ee 0 +
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5.
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Inositol:
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It is a sugar alcohol of 6 OH groups
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Term
It presents in high concentration in bran and it combines with 6
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Term
molecules of phosphoric acid to give phytic acid. Phytic acid
Definition
Term
forms insoluble iron
Definition
calcium and magnesium salts (phytate) which
Term
hinder absorption of Ca?*
Definition
Mg?’ and iron in the intestine.
Term
It presents in high concentration in heart and muscles tissues
Definition
so it
Term
is called muscle sugar
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It is considered a member of vitamin B complex because it is
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Term
essential for synthesis of phospholipids
Definition
phosphatidylinositol.
Term
II. Oligosaccharides
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Term
A. Disaccharides
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1- Reducing Disaccharides: ni CH ES
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+ It has a free aldehyde group {anomeric carbon)
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> Maltose
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> Lactose
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2. Non-reducing Disaccharides:
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* It has no free aldehyde group (anomeric carbon)
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> Sucrose
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Term
1- Reducing Disaccharides:
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A) Maltose (malt sugar):
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Term
+ It consists of 2 a-glucose units linked by a-1
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4-glucosidic
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linkage
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* It is a reducing disaccharide.
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+ It gives osazone called maltosazone (Rosette shaped).
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* It is produced during digestion of starch by amylase enzyme.
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+ It is hydrolyzed in human intestine by maltase enzyme.
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Term
B) Lactose (milk sugar) : el oy
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=- on
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- It is formed of B-galactose and a-glucose linked by B-1
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4-glucosidic
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linkage.
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Term
- ita reducing disaccharide
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forms lactosazone that has >
Term
sun ray appearance.
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- Itis digestible by lactase into glucose and galactose.
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- It is excreted physiologically in urine of pregnant and lactating
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females (lactosuria) and must be differentiated from pathological
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glucosuria caused by diabetes mellitus by:
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1. Osazone test.
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2. Barfoed's test.
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3. Specific enzymatic reaction such as glucose oxidase.
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It is the most suitable sugar for baby feeding as a sweetener for
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milk because:
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. It is the least sweet sugar so that the baby can nurse a large amount
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of mother’s milk without getting his appetite lost.
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Term
. It is non-fermentable sugar
Definition
so it does not form gases and not cause
Term
colic to the infant.
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Term
. It has a laxative effect and prevents constipation.
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4. Unabsorbed sugar is used as a food for large intestinal bacteria
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Term
that form a number of vitamins that benefits the baby.
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. It is easily digested and helps absorption of the minerals of milk.
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r o.
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ri a. N
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day
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b
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cnn
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e -
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2. Non-reducing Disaccharides:
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Sucrose (Cane or Table sugar):
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It is table sugar and sugar of cane and molasses.
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It is formed of a-glucose linked to B-fructose by a-B-1
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2-linkage.
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The 2 anomeric carbons (C1 of glucose and C2 of fructose) are
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Term
involved in the linkage
Definition
therefore it is:
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Non-reducing sugar.
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Non osazone forming.
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It is hydrolyzed by sucrase enzyme into equal amounts of glucose
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and fructose.
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III- Polysaccharides:
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Definition: They contain more than 10 monosaccharide units per
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molecule.
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Classification:
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- They are classified into:
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1-Homopolysaccharides
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They produce only one type of monosaccharides on hydrolysis
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Term
2-Heteropolysaccharides
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They produce several types of sugars on hydrolysis.
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Term
1. Homopolysaccharides
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Term
-They are named according to the type of that
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monosaccharide
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-Pentosans_ = Pentoses
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-Hexosans = Hexoses
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Hexosans
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Term
1. Glucosans:
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Term
@ Starch
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Term
@ Dextrins
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Term
@ Dextran
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Term
@ Glycogen
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Term
@ Cellulose
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Term
2.Fructosans: Inulin
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Term
3. Galactosans: Agar-Agar
Definition
Term
4. N-acetyl-glucosans: Chitin
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Term
Comparison between Starch
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Glycogen and Cellulose:
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Starch Glycogen Cellulose
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Term
1. Nature:
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Term
Stored form of carbohydrate in[Stored form of] Structural form of]
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Term
plants. The core is amylose carbohydrates in animals. |carbohydrate in plant cells.
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Term
(20%) and the shell is amylopectin
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Term
(80%).
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Term
12. Source:
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Term
Cereals
Definition
and tubers, ¢.g., potatoes. _|Muscles and liver Linen and cotton
Term
oly
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Term
[Amylose is water soluble
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Term
amylopectin is insoluble.
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Water soluble.
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Water insoluble.
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4. Nature of the chains:
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‘Amylose is helical straight chain (o-|
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Term
glucose units linked by «-I
Definition
4-
Term
glucosidic bonds).
Definition
Term
JAmylopectin is branched chain (o-|
Definition
Term
glucose units linked by a-1
Definition
4- and a-
Term
1
Definition
6-glucosidic bonds).
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Branched chain similar}
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to amylopectin but its|
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Term
trees are shorter and have}
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Term
more branches — than|
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amylopectin tree.
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Straight chain (large number]
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Term
of B-glucose units linked by
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Term
B-1
Definition
4- glucosidic bonds).
Term
5. Digestibility:
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Term
Is hydrolyzed by HCI or amylase into|
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Term
Jdextrins and maltose.
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Digestible by amylase
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into dextrins and
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Term
Non-digestible but HCI
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hydrolysis gives cellobiose.
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maltose.
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Term
«>
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Cellulose =. we
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@ It is indigestible in humans because of lack of enyzmes that
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Term
hydrolyze B- glycosidic linkage
Definition
but it is very essential in human
Term
food because:
Definition
Term
1. Prevention of constipation by increasing the bulk of stools.
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Term
2. Its fermentation by intestinal bacteria give some water soluble
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Term
vitamins and volatile fatty acids that is anticancer for colon cells.
Definition
Term
3. It adsorbs toxins present in foods and prevents its absorption.
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Term
4
Definition
It adsorbs cholesterol present in foods and decrease its
Term
absorption.
Definition
Term
5
Definition
It increases gastric emptying time, and so prevents rapid rise of
Term
blood glucose level (This is beneficial for dieters and diabetics).
Definition
Term
6. It prevents cancer colon (volatile fatty acids produced from its
Definition
Term
fermentation
Definition
decrease contact time by stimulating prestalsis and
Term
by adsorbing carcinogens on its surface).
Definition
Term
Dextran
Definition
Term
@ It is synthesized by certain bacteria.
Definition
Term
4 It has a great biochemical importance.
Definition
Term
1. It is used as plasma substitute to restore blood pressure in
Definition
Term
cases of shock.
Definition
Term
2. Combination of dextran with iron used for treatment of iron
Definition
Term
deficiency anemia by injection.
Definition
Term
3. Sodium dextran sulfate is an anticoagulant.
Definition
Term
i LF
Definition
Term
Iron Deficiency ce
Definition
Term
Anemia ner mr ws
Definition
Term
O e o a
Definition
Term
2. Heteropolysaccharides
Definition
Term
They are polysaccharides that on hydrolysis produce several types of sugars.
Definition
Term
I. Non-nitrogenous heteropolysaccharides:
Definition
Term
IL. Nitrogenous heteropolysaccharides: Contain sugar amines
Definition
Term
A) Neutral nitrogenous (Glycoproteins): Does not contain
Definition
Term
uronic acids
Definition
Term
B) Acidic nitrogenous (Mucopolysaccharides
Definition
Glycosaminoglycans
Term
& Proteoglycans) Contain uronic acids
Definition
Term
> Sulfur-free: Hyaluronic acid
Definition
Term
> Sulfur-containing: Chondroitin sulfate
Definition
Heparin.
Term
A- Neutral Nitrogenous Heteropolysaccharides:
Definition
Term
(Glycoproteins)
Definition
Term
- They do not contain uronic acids or sulfate groups.
Definition
Term
- They are formed of a large protein core and smaller branched
Definition
Term
chains of carbohydrate.
Definition
Term
B- Acidic Nitrogenous Heteropolysaccharides:
Definition
Term
(Mucopolysaccharides)
Definition
Term
Y N
Definition
Term
conjugated form
Definition
Term
with proteins
Definition
Term
{Proteoglycans)
Definition
Term
* Proteoglycans: (mucopolysaccharides + proteins).
Definition
Term
* They consist of very small core protein molecule and a huge
Definition
Term
carbohydrate tree that is highly complex in the form of repeating
Definition
Term
disaccharide units.
Definition
Term
free soluble form
Definition
Term
{hyaluronic acid)
Definition
Term
Acidic Nitrogenous Heteropolysaccharides:
Definition
Term
Sulfur free Mucopolysaccharides
Definition
Term
Hyaluronic acid
Definition
Term
It is formed of N-acetyl glucosamine linked to glucuronic acid. It is formed
Definition
Term
of 400 - 4000 repeating disaccharide units.
Definition
Term
Hyaluronic acid is unique among the GAGs in that:
Definition
Term
1- It is un-sulfated
Definition
Term
2- It is not found covalently attached to proteins as a proteoglycan
Definition
Term
3- Only GAG present both in animals and bacteria
Definition
Term
Biochemical importance:
Definition
Term
1
Definition
Term
. The molecule is coiled and entwined making a very firm gel which
Definition
Term
prevents bacterial invasion of the skin.
Definition
Term
. It is present in connective tissue matrix
Definition
vitreous humor of the
Term
eye
Definition
in the skin, synovial fluid, around the ovum, and in the
Term
umbilical cord to preserve the full-form of these structures.
Definition
Term
. Hyaluronic acid imbibes water and forms a incompressible
Definition
Term
substance due to the presence of several OH groups causing
Definition
Term
repulsion between carbohydrate units enabling the molecule to
Definition
Term
perform its function as lubrication in joint synovial fluids.
Definition
Term
Hyaluronidase Enzyme or Spreading factor:
Definition
Term
@ It is the enzyme that hydrolyzes hyaluronic acid.
Definition
Term
O It is present in sperms to help penetration of the ovum and
Definition
Term
fertilization.
Definition
Term
@ It is present in some virulent strains of bacteria that are able to
Definition
Term
spread through infected wounds. .
Definition
Term
0 It is present also in snake and scorpion venom.
Definition
Term
@ It is used in medicine to treat fibrosis and to dissolve mucus.
Definition
Term
Acidic Nitrogenous Heteropolysaccharides:
Definition
Term
Sulfated Mucopolysaccharides
Definition
Term
Chondroitin Sulfate
Definition
Term
a It is formed of sulfated N-acetyl-galactosamine and glucuronic
Definition
Term
acid or iduronic acid.
Definition
Term
4 Present in cornea of the eye
Definition
tendons, ligaments, bones,
Term
cartilage and connective tissue matrix.
Definition
Term
4 They absorb water
Definition
form incompressible substances by means of
Term
their ionizable OH and sulfate groups
Definition
creating negative charges
Term
leading to repulsion between the molecules.
Definition
Term
eco
Definition
Term
ed
Definition
Term
Ligemento|
Definition
Term
Acidic Nitrogenous Heteropolysaccharides: =
Definition
Term
. en
Definition
Term
Sulfated Mucopolysaccharides Deep Ven Thrombosia
Definition
Term
Heparin uy E |
Definition
Term
* It is formed of a long repeat of sulfated a-glucosamine and sulfated
Definition
Term
iduronic acid.
Definition
Term
* Biomedical significance: idee
Definition
Term
1. It is an anticoagulant produced by mast cells and prevents
Definition
Term
intravascular clotting. Therefore
Definition
it is used in cases of increased
Term
coagulability
Definition
e.g deep venous thrombosis.
Term
2. It binds to and liberates lipoprotein lipase enzyme to clear the
Definition
Term
turbid plasma from the absorbed lipids after meals.
Definition
Term
3. It participates in cell-cell and cell-matrix interaction
Definition
cell
Term
proliferation
Definition
apoptosis and differentiation. uss e
Term
. yr
Definition
Term
wT)
Definition
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