1. Chemistry of Carbohydrates

2. Chemistry of Carbohydrates
Definition of carbohydrates:
First Definition (Old definition):
Carbohydrates are substances containing carbon, hydrogen and oxygen having the general formula CnH2nOn.
(C3 H6 O3)
Hydrogen and oxygen are present in 1:2 ratio the same ratio as water, so the French called them “Hydrates de Carbon”, i.e., carbo-hydrates Cn(H2O)n.

3. The old definition is inaccurate because:
There are substances which are not carbohydrates but have the formula CnH2nOn , e.g., acetic acid CH3COOH (C2H4O2) and lactic acid.
There are some carbohydrates, which do not have this general formula, e.g., amino sugars and deoxy sugars

4. Second Definition (new definition): Carbohydrates are aldehyde (CHO) or ketone (C=O) derivatives of polyhydric alcohols (have more than one OH group) or compounds which yield these derivatives on hydrolysis.

5. Importance of carbohydrates:
The chief source of energy.
Important structural components in animal and plant cells.
Important part of nucleic acids and free nucleotides and coenzymes.
Major antigens are carbohydrates in nature, e.g., blood group substance.
Biological role as a part of hormones and their receptors and enzymes.

6. Classification of carbohydrates
According to the number of sugar units in the molecule there are three type:
Monosaccharides (simple sugars): They contain one sugar unit, i.e., and the simplest form of sugars and cannot be further hydrolyzed. They represent the end products of carbohydrate digestion in the human body.
Oligosaccharides: They contain 2 – 10 monosaccharide units per molecule and give monosaccharides on acid hydrolysis.
Polysaccharides: They contain more than 10 monosaccharide units per molecule and give monosaccharides on acid hydrolysis.

7. Monosaccharides
They are classified according to the number of carbon atoms into five important groups.
Each of these groups is subdivided according to the type of functional chemical group into: Aldoses (sugars containing aldehyde group) and Ketoses (sugars containing ketone group).

8. 1. Bioses: are monosaccharides containing 2 carbon atoms,
Glycolaldehyde

9. 2. Trioses: are monosaccharides containing 3 carbon atoms, e.g.,
A- Aldotriose: Example is

10. B- Ketotriose: e.g.,
Dihydroxyacetone, the hydroxylated form of Acetone

11. 3. Tetroses: are monosaccharides containing 4 carbon atoms:
Aldotetroses:

12. B- Ketotetroses:

13. 4. Pentoses: they contain 5 carbon atoms
4. Pentoses: they contain 5 carbon atoms. Ribose is the most important pentose because it enters in the structure of DNA and RNA and important free nucleotides such as ATP and coenzymes

14. A- Aldopentoses:

15. B- Ketopentose:

16. 5.Hexoses: are monosaccharides containing 6 carbon atoms.
They are the most important monosaccharides particularly glucose:

17. A- Adohexoses:

18. B- Ketohexoses:

19. Asymmetric carbon atom
- Asymmetric carbon atom is the carbon atom attached to which 4 different groups or atoms.

20. Ordinary light vibrates in all directions.
Ordinary light can be changed to plane polarized light by passing it through a prism made of calcium carbonate .
Plane polarized light vibrates in one plane and direction.

21. Optical activity is determined by polariscope or polarimeter that is consisted of:
A light source (usually a sodium lamp).
A polarizer that is a prism made of calcite.
A narrow slit path to bring forth a parallel beam of light.
A polarimeter tube to contain the solution of the substance tested (mostly 1.0 decimeter in length).
A scale graduated in increasing positive (+) degrees from 0.0 on its right part and in increasing negative (-) degrees from 0.0 on its left part.

22. Importance of asymmetric carbon atom: Any compound containing asymmetric carbon atom has the following two properties:
Isomerism is created around it.
It makes the compound optically active

23. Optical activity
Definition: It is the ability of the sugar to rotate the plane of the plane polarized light.
The sugar that rotates the light to the right is called dextrorotatory (d or +) such as glucose, galactose and starch and that rotating light to the left is called levorotatory (l or -) such as fructose and invert sugar.

24. Factors affecting optical activity:
Type and Concentration of the substance and type of solvent.
Type of light used and temperature.
Length of polarimeter tube in decimeters.

25. Specific rotation:
It is the observed angle of deviation of the plane polarized light in degrees from the straight path.
It is measured when the solution of the substance or the sugar dissolved in water is introduced in the path of the plane polarized light under the following conditions.
The light source used is sodium light, the temperature is 20oC, the concentration is 100 gm/ 100 mL and the polarimeter tube is one decimeter in length.

26. Each optically active substance has a characteristic specific rotation such as, -glucose is +112, -glucose is +19 and fructose is

27. Uses of polariscope and importance of optical activity:
Identify an unknown optically active substance.
Identify whether the substance is optically active or not.
Identify whether the substance is levorotatory or dextrorotatory.
Determine the concentration of the substance.
Differentiate between glucosuria and lactosuria. This is important in late pregnancy to differentiate between diabetes mellitus (glucose) and the normal appearance of lactose produced by the mammary glands in urine.

28. Mutarotation:
It is a temporary change in the specific rotation of the sugar when it is freshly prepared.
Mutarotation is due to the presence of a free anomeric carbon (C1 in aldoses, C2 in ketoses).

29. For example, -glucose when freshly prepared has a specific rotation of +112, then the specific rotation decreases gradually till it stabilizes at (point of equilibrium)
-glucose when freshly prepared has a specific rotation of +19, then the specific rotation gradually increases till it is stabilizes at (point of equilibrium)

30. In solution, -glucose changes to -glucose through the straight chain form and vice versa till the point of equilibrium is reached, where the solution is composed of: 2/3 -glucopyranose, 1/3 -glucopyranose, 1% -glucose ( and -glucofuranose) and % open chain form (Reactive form).

31. Cyclic structure of monosaccharides

32. Steps of the cyclic form construction:
Condensation of a molecule of H2O with the aldehyde or keto group of the sugar to form aldenol or ketonol group.
The OH group from the aldenol group condenses with the OH on C4 (Furanose) or C5 (Pyranose) of the aldo-sugar to forms a ring or hemi-acetal structure with the liberation of H2O again. Keto-sugar condenses only with C5 (Furanose) or with C6 (Pyranose).

33. When the remaining OH on the aldehyde or the keto carbon atom in the cyclic form is located on the right side, the sugar form is called -sugar and if it is located on the left side the sugar is called -sugar.

36. Haworth's projection formula:
Because Fisher’s formula could not explain some of the chemical and physical characteristics of sugars, Haworth put forth his projection formula.
C and O atoms of the ring are drawn in the plane of the page.
H and OH or other side groups are written on perpendicular plane.
All groups located on the left side of fisher’s are written upwards. All groups located on the right side of fisher’s are written downwards.
The radical of the molecule (the extra-cyclic part) is written upwards in D sugar and inside the ring (or down wards) in L-sugar.

40. Isomerism
Isomers are substances which have the same molecular formula but differ in distribution of their atoms into groups or distribution of these groups and atoms in the space around carbon atoms. There are 2 types of isomerism;
Structural isomerism.
Stereo-isomerism.

41. 1. Structural isomerism:
They are isomers that have different structure due to different ways of arrangement of atoms and groups forming the molecule. Types of structural isomerism are four as follows:

42. a. Chain isomerism.
These are isomers that have different structures due to different ways of attachment of carbon atoms forming the molecule,

43. b. Positional isomerism:
These are isomers that have the same carbon skeleton but differ in the position of the substituent groups, e.g.,

45. C.Functional group isomerism:
- These are isomers that have the same carbon skeleton, the same position of substituent group but have different functional group (aldo-/keto-). c
Aldehydes such as;
Glyceraldehyde,
Erythrose,
Ribose, Xylose
Glucose
Ketones such as;
Dihydroxyacetone,
Erythrulose,
Ribulose, Xylulose,
Fructose

46. d. Ring isomerism:
Pyran/furan forms such as glucopyranose and glucofuranose, and fructopyranose and fructofuranose.

47. 2. Stereo-isomerism:
They are molecules having the same structure but differ in position of their different groups and atoms in the space,
The number of stereoisomers = 2n, where n is the number of asymmetric carbon atoms. There are four types of stereo-isomerism as follows:

48. a. D and L isomerism
They differ in distribution of H and OH groups around the sub-terminal asymmetric carbon atoms.
D form has the OH group to the right of the sub-terminal carbon atom .whereas, it is on the left in L form.
This difference make the two forms (D and L) mirror image to each other due to the change of the position of all H and OH groups into the opposite direction of D form in L form.

50. b. Epimers:
They are stereoisomers which differ in distribution of H and OH groups around a single asymmetric carbon atom other than the anomeric and DL-form creating carbon before the last i.e., without difference on other carbon atoms.
Ribose is an epimer to each of arabinose and xylose. Glucose is an epimer to each of mannose and galactose.

51. Chemistry of carbohydrates
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55. Arabinose and xylose as well as galactose and mannose are not epimers to each other
because they differ around distribution of H and OH in more than one asymmetric center.

56. c. Anomers:
They are stereoisomers which differ in distribution of H and OH group around the asymmetric anomeric carbon atom C1 in aldoses or C2 in ketoses after cyclization of the molecule, e.g.

57. d. Geometric isomerism:
It involves distribution of atoms or groups around the axis of a double bond in the space.

58. Physical Properties of Monosaccharides:
All monosaccharides are soluble in water.
All monosaccharide show the property of optical activity.
All monosaccharides can exist in α and β forms.
All monosaccharides undergo mutarotation.

59. Sugar acids Sugar alcohols Amino sugars Deoxy sugars
Sugar derivatives
Sugar acids
Sugar alcohols
Amino sugars
Deoxy sugars

60. 1.Sugar acids
Produced by oxidation of carbonyl carbon to carboxylic group.
Or by oxidation of last hydroxy carbon to carboxylic group.
Or by oxidation of both.

61. 1.Aldonic

62. 2-Uronic

63. 3-Aldaric

64. 2-sugar alcohols:
Reduction of monosaccharides gives sugar alcohols.

65. Ribose reduction gives Ribitol that is a part of the structure of vitamin B2
(Riboflavin),

66. Reduction of glucose gives sorbitol or glucitol that enters in medical industries

67. Fructose reduction gives Sorbitol or Mannitol.

68. Inositol: It is a hexahydric alcohol (6 OH groups),
- It presents in high concentration in heart and muscles tissues, so it is called muscle sugar

69. 3-Amino sugars :
Replacing OH group on C2 by an amino group (NH2) produces them.

71. 4-Deoxysugars: These are sugars in which OH group is replaced by H.
1. At C2 gives Deoxy sugar proper
deoxyribose that enters in structure of DNA.,

72. 2. At C6 gives methyl pentoses (Methylose), e. g
2. At C6 gives methyl pentoses (Methylose), e.g., L-galactose gives L-fucose and, L-Mannose gives L-rhamnose,

73. Glycosides
They are products of the reaction of the OH group of the anomeric carbon with either another OH group or NH2 group from another compound producing compounds called glycosides.
The other compounds may be another sugar, called glycan or a non-sugar, called aglycan. The glycosides can be named according to the type of sugar, e.g., glucose forms glucosides and galactose forms galactosides, …etc.

74. Types of Glycosides:
I. Glycosides containing R–O–R (ether linkage):
Disaccharides: e.g., lactose and maltose see later.
II. R-N-R Glycosides:
Nucleotides: The sugar is ribose or deoxyribose linked with purine and pyrimidine bases.
Glycoproteins.

76. Oligosaccharides Disaccharides: 1- Reducing Disaccharides
It has a free aldehyde group (anomeric carbon)
2- Non-reducing Disaccharides:
It has no free aldehyde group (anomeric carbon)

77. 1- Reducing Disaccharides:
A-Maltose (malt sugar):
It consists of 2 -glucose units linked by -1,4-glucosidic linkage,

78. It has a free aldehyde group (anomeric carbon), therefore it :
exists in  and  forms.
exhibits mutarotation.
is a reducing disaccharide.
gives osazone called maltosazone (Rosette shaped).
is a fermentable sugar, due to -glucosidic bond.
It is produced during digestion of starch.
It is hydrolyzed by acids and in human intestine by maltase enzyme.

79. B-Isomaltose:
It is formed of 2 -glucose linked by -1,6-glucosidic linkage.

80. C-Lactose:
It is formed of -galactose and -glucose linked by -1,4-glucosidic linkage

81. It is the milk sugar with free aldehyde making it a reducing disaccharide.
lactosazone forming (Puff-like), and having  and -forms.
It is digestible by lactase into glucose and galactose.
It is excreted in urine of pregnant and lactating females

82. It is the most suitable sugar for baby feeding as a sweetener for milk because:
It is the least sweet sugar so that the baby can nurse a large amount of mother’s milk without getting his appetite lost.
Because it has a -glycosidic linkage it is non-fermentable sugar, so it does not form gases and not cause colic to the infant.
It has a laxative effect and prevents constipation and non-irritant to the stomach and does not induce vomiting.
Unabsorbed sugar is used as a food for large intestinal bacteria that form a number of vitamins that benefits the baby.

83. D) Cellobiose:
It is formed of 2 -glucose units linked by -1,4-glucosidic linkage.
Reducing disaccharide.
It is the building unit of cellulose.
It is non-fermentable, indigestible.
shows mutarotation .
have  and -forms.

85. 2. Non-reducing Disaccharides:
A. Sucrose:

86. It is table sugar and sugar of cane and molasses and is formed of -glucose linked to -fructose by --1,2-linkage. It is a fermentable sugar.
The 2 anomeric carbons (C1 of glucose and C2 of fructose) are involved in the linkage(no free groups) so it is:
Non-reducing sugar.
Non osazone forming.
Not mutarotating.
Not having  or -forms.

87. It is a dextrorotatory sugar but when it is hydrolyzed by sucrase enzyme or by acid hydrolysis (HCl) the mixture of sugars produced is levorotatory.
This is because the levorotatory power of fructose (-92.5) cancels the dextrorotatory power of glucose (+52.5) since they are at equal proportions in the product. This is why this sugar is called invert sugar.
Sucrase enzyme is therefore, also called invertase enzyme.

88. Differences between sucrose and invert sugar:
Formed of: -glucose and -fructose linked by 1,2-linkage.
An equimolar mixture of free -glucose and -fructose.
Optical activity: Dextrorotatory.
Levorotatory.
Reductive ability: Non-reducing (no free CHO or C=O groups).
Reducing (there are free CHO and C=O groups)
Digestion: Needs digestion (sucrase).
No further digestion.
Other names: Cane and table sugar.
Bees honey and invert sugar.

89. B. Trehalose:
It is formed of 2 -glucose units linked by -1,1-glucosidic linkage.
Present in a highly toxic lipid extracted from Mycobacterium tuberculosis.

90. Trisaccharides
Rhafinose:
Presents in molasses. It is a trisaccharide formed of one unit of each of glucose, galactose and fructose.
Tetrasaccharides
Stacchyose:
- Presents in onions. It is formed of 2 galactose units and one unit of each of glucose and fructose.

91. Polysaccharides They are classified into: A-Homopolysaccharides
B-Heteropolysaccharides.

92. A-Homopolysaccharides
They yield only one type of monosaccharides on hydrolysis and they are named according to the type of that monosaccharide, e.g.,
Hexosans + H2O  Hexoses
Pentosans + H2O  Pentoses

93. Hexosans: I. Glucosans: They produce only glucose on hydrolysis.
They include; starch, dextrins, dextrans, glycogen and cellulose,

94. A. Starch:
It is the stored form of carbohydrate of plants. It never exists in animals.
It is present in cereals such as wheat and rice and tubers such as potatoes.
It is in the form of starch granules. The core of the granule is amylose (20%) and the shell is amylopectin (80%).
Due to its high molecular weight it forms colloidal solution in hot water.

95. 1. Amylose:. Straight chain compound present in the form glucose units linked by -1,4-glucosidic bond of a helix formed of a large number of - glucose.
It forms the inner part of starch granules

96. Amylopectin:
It forms the outer coat of starch granule and is insoluble in water.
It is branched chains formed of a large number of -glucose units linked by -1,4-glucosidic linkage along the branch and by -1,6-glucosidic linkage at the branching point that occur every glucose units. Due to its high molecular weight, it forms a colloidal solution.
Starch can be hydrolyzed by HCl or amylase.

98. B. Dextrins:
Products of hydrolysis of starch and include amylodextrin, erythrodextrin, achrodextrin which form color with iodine
They have sweet taste.
They are easily digested than starch as in corn and rice syrup.

99. C. Dextran:
A compound formed of -glucose units linked by -1,4, -1,3- and -1,6-linkage present in the form of a network that is synthesized by certain bacteria having sucrose in its media.
It has a great biochemical importance,
It is used as plasma substitute to restore blood pressure in cases of shock.
Iron used for treatment of iron deficiency anemia is used as dextran ferrous sulfate intramuscular injection.
Sodium dextran sulfate is an anticoagulant.

100. D. Glycogen:
It is the stored form of carbohydrate in animal, particularly in muscles and liver.
Its structure is similar to amylopectin a branched tree with -1,4-glucosidic linkage along the branch and -1,6-glucosidic linkage at the branching point.
The glycogen tree is shorter and more branched (a branch point every 8-10 glucose units) than amylopectin.
It is digestible because human amylases hydrolyze -glucosidic linkage.

101. E. Cellulose:
It is a structural polysaccharide and forms the skeleton of plant cells and does not enter in animals cell structures.
It is a straight chain molecule formed of a large number of -glucose units linked by -1,4-glucosidic linkage.
It is water insoluble and enters in structure of cotton and paper
It is the major food for herbivorous animal where it is fermented into volatile fatty acids.
It gives cellobiose on hydrolysis with HCl.

102. It is indigestible but is very essential in food for:
Prevention of constipation by increasing the bulk of stools.
Its fermentation by large intestinal bacteria give volatile fatty acids that is anticancer for colon cells and gives also some water soluble vitamins.
It adsorbs toxins present in foods and prevents its absorption into the body.

103. Starch
Glycogen
Cellulose
Nature:
Stored form of carbohydrate in plants.
Stored form of
carbohydrates in animals.
Structural form of carbohydrate in plant cells but prevents constipation in human.
Source:
Cereals, e.g., wheat, rice, and tubers, e.g., potatoes.
Muscles and liver
Linen and cotton are nearly pure cellulose.
Solubility:
Amylose is water soluble and amylopectin is insoluble.
Water soluble forming colloidal solution.
Water insoluble.
Nature of the chains:
Amylose is helical straight chain (-glucose units linked by -1,4-glucosidic bonds). Amylopectin is branched chain (-glucose units linked by -1,4- and -1,6-glucosidic bonds).
Branched chain similar to amylopectin but its trees are shorter and have more branches than amylopectin tree.
Straight chain (large number of -glucose units linked by -1,4- glucosidic bonds).
Reaction with iodine:
Amylose gives blue color and amylopectin gives red color.
Gives red color.
No color.
Digestibility:
Is hydrolyzed by HCl or amylase into dextrins and maltose.
Digestible by amylase into dextrins and maltose.
Non-digestiblebut HCl hydrolysis gives cellobiose.

104. II. Fructosans: Inulin:
They are formed of fructose as a building unit such as Inulin.
Inulin:
It is formed of fructose only and present in onions.
It is not metabolizible in human body, therefore, it is used in evaluation of kidney function as a part of inulin clearance test.

105. III. Galactosans:
- They are formed of galactose as the building units such as agar-agar.
- Biochemical importance:
It is used for growth of bacteria and mammalian cells in culture.
It imbibes water and increases intestinal contents to prevent and treat constipation.
Some electrophoresis gels is formed of it.

106. IV. N-acetyl-glucosan:
It is a homopolysaccharide formed of -N-acetyl-glucosamine units such as chitin of insects.
Chitin:
It is a homopolysaccharide formed of -N-acetyl-glucosamine units linked by -1,4-glucosidic linkage present in the exoskeleton of insects.

108. B-Heteropolysaccharides
They are polysaccharides that on hydrolysis produce several types of sugars. There are two types:
Non-nitrogenous heteropolysaccharides
nitrogenous heteropolysaccharides.

109. 1-Plant gums : A-Non-nitrogenous heteropolysaccharides:
They do not contain sugar amines such as pectin and plant gums.
1-Plant gums :
They are exudates of plants that do not contain amino sugars.
They contain pentoses, hexoses and uronic acids, e.g., Arabic gum which is rich in arabinose.
They are emulsifying agents.

110. 2. Pectin:
They are present in fruits and are responsible for settling of jams.
They are formed of pentoses, hexoses, uronic acids mainly galacturonic acid.
They are water soluble formed from a water insoluble compound called pectose present in raw fruits which is transformed into pectin by the action of sunlight, heat and pectase enzyme when fruits are ripened.

111. Biochemical importance of pectin:
Emulsifying reagents.
Demulcents.
Responsible for settling of jams.
They increase in size when they absorb water forming a jell and so they are used in the treatment of infantile diarrhea.

112. B-Nitrogenous heteropolysaccharides:
They contain sugar amines and are of two types:
Neutral nitrogenous heteropolysaccharides
Acidic nitrogenous heteropolysaccharides

113. 1-Neutral nitrogenous heteropolysaccharides
Glycoproteins or mucoproteins:
They do not contain uronic acids or sulfate groups (which give acidic characteristics).
They are formed of a large protein core to which are attached smaller branched or unbranched chains of carbohydrate.
The carbohydrate present include:
Hexoses: mannose, galactose and glucose
Pentoses: xylose and arabinose.
Amino sugars: glucosamine and galactosamine.
Deoxysugars: L-fucose, L-rhamnose and sialic acid.

114. Blood group substances A and B antigens.
Distribution: Glycoproteins are widely distributed in mammalian tissues. They include:
Mucins of epithelium lining of gastrointestinal, urogenital and respiratory tracts are lubricant and protective.
Cell membranes where they play an important part in cell-cell attachment.
Blood group substances A and B antigens.
Mineral and vitamin transporting protein, e.g., trasferrin.
Immunoglobulins (antibodies), IgG, IgM, IgA….
Some hormones, e.g., anterior pituitary hormones: LH and FSH.
Some enzymes such as peptidases and alkaline phosphatase.
Intrinsic factor that is responsible for vitamin B12 absorption.
Structural function as a part of collagen of connective tissue.

115. 2. Acidic nitrogenous heteropolysaccharides
A-Sulfur-free mucopolysaccharides:
Their sugar units are not sulfates, e.g., hyaluronic acid.
B- Sulfur-containing mucopolysaccharides:
Their sugar units are sulfated ,e.g.,chondroiten sulfate , Heparin

116. Hyaluronic acid: -
It is formed of -D-N-acetyl glucosamine linked to -D-glucuronic acid by alternating -1,3- and -1,4-glycosidic linkages.

117. Biochemical importance:
The molecule is coiled and entwined making a very firm gel which prevents bacterial invasion of the skin.
It is present in connective tissue matrix, vitreous humor of the eye, in the skin, synovial fluid, around the ovum, and in the umbilical cord to preserve the full-form of these structures.
Hyaluronic acid imbibes water and forms a incompressible substance due to the presence of several OH groups which creates negative charges causing repulsion between carbohydrate units enabling the molecule to perform its function as lubrication in joint synovial fluids an.

118. Hyaluronidase Enzyme or Spreading factor: It is the enzyme that hydrolyzes hyaluronic acid.
It is present in sperms to help penetration of the ovum and fertilization.
It is present in some virulent strains of bacteria that are able spread through infected wounds.
It is used in medicine to treat fibrosis and to dissolve mucus.

119. 1-Chondroitin sulfate: it is of three types as follows:
B. Sulfur-containing mucopolysaccharides
1-Chondroitin sulfate: it is of three types as follows:
Chondroitin sulfate A:
It is formed of -N-acetyl-galactosamine-4-sulfate and -glucuronic acid linked by alternating -1,3- and -1,4-glycosidic linkages.

120. Chondroitin sulfate B:
It is formed of -N-acetyl galactosamine-4-sulfate and -L-iduronic acid linked by alternating -1,3- and -1,4-glycosidic linkages.
L-iduronic acid is the C5 epimer of D-glucuronic acid, i.e., COOH group at C5 is inside the ring,

121. Chondroitin sulfate C:
It is formed of -N-acetyl galactosamine-6-sulfate and -glucuronic acid linked by alternating -1,3- and -1,4-glycosidic linkages.
Present in cornea of the eye, tendons, ligaments, bones, cartilage and connective tissue matrix.
They absorb water, form incompressible substances by means of their ionizable OH and sulfate groups, creating negative charges leading to repulsion between the molecules.

123. 2. Heparin:
Structure: It is formed of a long repeat of sulfated -glucosamine and sulfated -L-iduronic acid linked by alternating - and -1,4-glycosidic linkages, synthesized on a core protein.
Source: It is produced by mast cells (kidney, lung, liver skin).

124. Function:
It is an anticoagulant and prevents intravascular clotting. It interferes with the activated clotting factors (thrombin, IX, X, XI and XII) in coagulation, through activation of antithrombin III that inhibits the intrinsic pathway of blood clotting. Therefore, it is used in cases of increased coagulability, e.g., cardiac ischemia or deep venous thrombosis.
It binds activates lipoprotein lipase enzyme (the plasma clearing factor) to clear the turbid plasma from the absorbed lipids after meals.
It regulates the action of the heparin-binding growth factors.
It has a structural role in extracellular matrix. It affects cell-cell and cell-matrix interaction to modulate development, cell proliferation, apoptosis and differentiation.

125. Chemistry of carbohydrates