Polysaccharides

1
Polysaccharides

• www.themegallery.com

2
By Dr. Batoul Izzularab
3
4
3
Polysaccharides

• Polysaccharides are long carbohydrate molecules
  of monosaccharide units joined together by
  glycosidic bonds. They range in structure from
  linear to highly branched.
• When all the monosaccharides in a polysaccharide
  are the same type, the polysaccharide is called a
  homopolysaccharide or homoglycan, but when more
  than one type of monosaccharide is present they
  are called heteropolysaccharides or heteroglycans.

4
General properties of polysaccharides

• They are formed from great number of
  monosaccharide units (more than ten unit)
  attached together by glucosidic bond.
• They are high molecular weight compound
• All give positive molish test
• All are nonreducing sugar
• All are optically active compound
• All are negative for ozazone test

5
General properties of polysaccharides

• All formed colloid solution i.e. insoluble in
  water , on hydrolysis they give a great number of
  monosaccharide unit
• They form specific color with iodine e.g. starch
  gives blue color with iodine
• Beside they are important nutritive mitral , they
  are important in manufacture of
• Textile
• Artificial silk
• Paper

6
Homopolysaccharide

• Starch
•  It is a homopolymer of glucose forming an a-
  glucosidic chain, called glucosan or glucan
• It is the most important dietary carbohydrate in
  cereals, potatoes, legumes and other vegetables.
• Starch never present in animals tissue

7
Starch

• Starch granules is formed of amylose (13-20)
  which has nonbranching helical structure , and
  amylopectin (80-85) , which consists of branched
  chains composed of 24-30 glucose residues united
  by a1?4 linkages in the chain and by a1?6
  linkages at the branched points

8
Starch

• Amylose (13-20)
• The amylose represents the inner part of starch
  granules.
• It has a non-branching helical coil structure,
  containing only a1?4 glycosidic link.
• It gives deep blue color with iodine.

9
Starch

• Amylose

• Amylose a1?4 linkage

10
Starch

• Amylopectin (80-85)
• This represents the outer layer of starch
  granules.
• It is a branched chain structure, containing both
  ? 1?4 glycosidic link (Straight chain and
  ?1-6bond (branch point)
• Each chain of amylopectin in composed of 25-30
  glucose units linked together by ?1-6 bond at the
  branch points.
• Amylopectin gives red color with iodine

11
Starch

• Amylopectin

• Amylopectin a1?6 linkages

12
Starch

• Acid hydrolysis of starch produces great number
  of glucose units
• Enzymatic hydrolysis of starch by salivary
  amylase
•  
• Starch ?amylodextrin ?achrodextrin ?maltose 

13
Dextrin

• Dextrins are produced during enzymatic hydrolysis
  of starch by salivary amylase and pancreatic
  amylase.
• They are -like starch- formed of glucose units
  attached together by ?1-4 and ? 1-6 glycosidic
  bonds.
• Their structure is simpler than starch.

14
Dextrin
15
Glycogen

• Glycogen is the store of carbohydrates in animal
  life called "Animal starch".
• It is present mainly in the liver and muscles and
  gives red color with iodine.
• Chemically, it a highly branched chain
  homopolysaccharide.

16
Glycogen

• Each chain is composed of 12-14 glucose units
  linked by ?1-4glycosidic link in the straight
  chain and ?1-6 link in the branch points. It
  resembles the amylopectin part of starch.
• Glycogen store in liver which function as a
  source of blood glucose maintenance during
  starvation and in between meals

17
Glycogen
18
Cellulose 

• It is a long straight non-branching chains of
  glucose units) ?-D-glucose), attached by?1-4
  glycosidic link.
• The straight chains are cross linked by
  hydrogen bonds.
• It is the chief constituent of the frame work of
  plants e.g. leaved vegetables, cotton, woodetc

19
Cellulose
20
Cellulose

• Properties
• Non-reducing homopolysaccharide.
• Gives no color with iodine.
• Not digested in the human GIT, because of the
  absence of hydrolytic enzymes that attack ?-link.

21
Cellulose

• Its presence in the diet is important, because it
  cannot be digested, so it forms the main bulk of
  stool, stimulating the intestinal movements, and
  preventing constipation.
• Cellulose is digested in the GIT of herbivores,
  thus acting as source of energy. The GIT of these
  animals contains microorganisms that produce
  cellulase enzyme

22
Inulin

• Inulin is a fructosan, formed of ?-fructose units
  attached by ?1-2 glycosidic link.
• It is present in plants e.g. root of dahlias,
  artichokes and other plants.
• It is not digested or metabolized by human GIT.
• Inulin clearance is one of the important
  physiological diagnostic tests for investigation
  and measurement of glomerular filtration rate
  (GFR) of the kidney.

23
Inulin
24
Chitin

• Chitin forms of the shells of crustaceans and
  exoskeleton of insects.
• It is formed of repeated N-acetylglucosamine units

25
Heteropolysaccharides

• Heteropolysaccharides are polysaccharides on
  hydrolysis give rise into different type of
  monosaccharide unit i.e. different of
  monosaccharide units
• Agar Agar
• Derived from certain sea weeds. It is used as
  culture media for bacterial growth. The main
  sugar unit is galactose.

26
Pectins

• These are Heteropolysaccharides containing
  arabinose, galactose, and galacturonic acid.
• They are present in fruits, like orange, lemons,
  apricotsetc.
• Pectins have gellation properties, hence used for
  treatment of infantile diarrhea.

27
Glycosaminoglycans (GAG), (mucopolysaccharides(

• Glycosaminoglycans are Heteropolysaccharides
  which are present abundantly in the human body.

28
Glycosaminoglycans (GAG), (mucopolysaccharides(

• They are characterized by
• Chemically, they are formed mostly of repeated
  disaccharides units that contain
• amino sugar (N-acetyl glucosamine or N-acetyl
  galactosamine)
• uronic acid (glucuronic acid or its 5 epimer
  iduronic acid

29
Glycosaminoglycans (GAG), (mucopolysaccharides(

• Most are present extracellulary except heparin.
• mostly they act as structural components of the
  connective tissue e.g. collagen, bones, elastin,
  etc
• They can also act as lubricants, because they
  have the property of holding water e.g. synovial
  fluid and vitreous humor of the eye.

30
Glycosaminoglycans (GAG), (mucopolysaccharides(

• Types
• GAGs are either sulfate free (Hyaluronic acid) or
  sulfate containing as chondroitin sulfate,
  heparin, heparan sulfate, keratan sulfate and
  dermatan sulfate.
•  

31
Hyaluronic Acid

• Structure
• Repeated disaccharide units, composed of
  glucuronic acid and N-acetyl glucosamine.
•  

32
Hyaluronic Acid

• Site
• Present in
• Synovial fluid.
• Vitreous humor of the eye.
• Skin and loose connective tissue.
• Cartilage
• Embyronic tissue.

33
Hyaluronic Acid

• Functions
• Gel made of hyaluronic acid has good resistance
  to compression, thus it acts as lubricant and
  shock absorber in the synovial fluid.
• It makes extra cellular matrix loose, because of
  its ability to attract water.
• It forms an important part of cementing ground
  substance.

34
Hyaluronidase Enzyme

• This enzyme hydrolyses hyaluronic acid, thus
  allowing invasive agents to penetrate the tissue.
• It is secreted by certain bacteria to help their
  invasion to tissue.
• Secreted by Cercaria (infective stage of
  bilharziasis) to help penteration of skin.

35
Chondroitin Sulfate

• Structure
• Repeated disaccharide units composed of
  Glucuronic acid and N-acetyl galactosamine
  sulfate. The sulfate group is either attached to
  carbon 4 forming chondroitin -4- sulfate or
  carbon 6 forming chondroitin -6- sulfate.
•  

36
Chondroitin Sulfate

• Site
• Cartilage, tendons, ligaments, bones.
• Aorta, skin, cornea.
• Functions
• It has a role in binding collagen of cartilage
  and holding its fibers together. Compressibility
  of cartilage in weight bearing is due to
  chondroitin sulfate.

37
Heparin

• Structure
• Disaccharide repeated units of
• Iduronic acid with sulfate on C2
• Glucosamine with sulfate on C3 and C6.

38
Heparin

• Site
• In the mast cells (intracellular compound (
• Function
• Anticoagulant
• Stimulates the release of lipoprotein lipase
  enzyme that hydrolyses the absorbed fats.

39
Heparan Sulfate

• It is like heparin in structure, but it
• (1) contains fewer sulfate groups and
• (2) Some glucosamines are acetylated.
• Function
• It is an extra cellular compounds, entering in
  the structure of receptors on cell surface.
• It participates in cell adhesion and cell-cell
  interaction.

40
Keratan Sulfate

• Structure
• The disaccharide unit is composed of
• (1) Galactose with sulfate on C6 and
• (2 (N-acetyl glucosamine with sulfate on C6. No
  uronic acid
• Site Cornea and cartilage .It plays a role in
  corneal transparency.
•  

41
Dermatan Sulfate

• Structure
• Disacchride units composed of
• L-Iduronic acid
• N-acetyl galactosamine with sulfate on C6.
• It is widely distributed in animal tissue,
  resembling chondroitin sulfate and Heparan
  sulfate.
• It has anti thrombotic properties similar to
  heparin.
•  

42
Proteoglycans and Glycoproteins

• Both are proteins containing carbohydrates but
  they contain different sugars, have different
  structures perform different functions and
  present in different sites.

43
Proteoglycans

• When proteins are attached to glycosaminoglycans
  (mucopolysaccharides), the compound is called
  Proteoglycans.
• They serve as ground substance associated with
  structural elements of tissue e.g. bones,
  cartilage, elastin, collogen etc.
• The glycosaminoglycans are present as long
  unbranched chains around a protein core.

44
Proteoglycans
45
Glycoproteins (Mucoproteins)

• These occur in many different situations in
  fluids and tissues, including cell membranes.
• They have protein core to which are attached
  carbohydrate chains which are
• short, composed of 2-15 sugar units, or often
  oligosaccharide units, and
• branched.

46
Glycoproteins (Mucoproteins

• Sugar present in glycoproteins include
• Hexoses Galactose and mannose.
• Pentoses Arabinose and xylose.
• Melthyl pentose (L-fucose
• Sialic acid.
• Acetyl hexosamines, N-acetyl glucosamines and
  N-acetyl galactosamines.
• They contain no glucose, no uronic acid or
  sulfate group.

47
Glycoproteins (Mucoproteins

• Functions
• Components of extra cellular matrix.
• Act as biological lubricants in mucin of the GIT,
  respiratory tract and urogenital tract
• Components of cell membrane as
• Blood group antigens, A, B, AB.
• Cell surface recognition receptors

48
Glycoproteins (Mucoproteins

• Functions
• Certain hormones are glycoproteins as Thyroid
  stimulating hormone (TSH) and human chorionic
  gonadotrophin HCG.
• Some enzymes are glycoproteins
• The immunologic components e.g.
  Immunoglobulins,complement factors, interferon
  ...etc are glycoproteins

49
Thank You!

• www.themegallery.com