1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India

2. SEP-SBI072-CP1-04 Introduction Programmes and Courses  SEP –SBI072-CP1- UN01

3. School of Science and Technology, Online Counseling Resource… Credits  Academic Inputs by Sonali Alkari Faculty YCMOU Nagpur Centre, Faculty LAD college P.G. D of Biotechnology Research officer Ankur Seeds Pvt Ltd sonalisa_alkari@yahoo.co.in Sonalisaal@rediffmail.com 3© 2008, YCMOU. All Rights Reserved.

4. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

5. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Discuss homo and hetero polysaccharides. Describe starch. Describe cellulose. Describe chitin. Describe glycogen

6. School of Science and Technology, Online Counseling Resource… Polysaccharide-1  Most carbohydrates found in nature occur as polysaccharides, polymers of medium to high molecular weight.  Polysaccharides, also called glycans, differ from each other in the identity of their recurring monosaccharide units, in the length of their chains, in the types of bonds linking the units, and in the degree of branching.  Polysaccharides (poly, means “many”) are important energy-storage and structural molecules.  They are formed of long chains of sugars, most commonly glucose. © 2008, YCMOU. All Rights Reserved.6

7. School of Science and Technology, Online Counseling Resource… Polysaccharide-2  Homopolysaccharides contain only a single type of monomer.  Heteropolysaccharides contain two or more different kinds  Some homopolysaccharides serve as storage forms of monosaccharides that are used as fuels; starch and glycogen are homopolysaccharides of this type.  Homopolysaccharides (cellulose and chitin, for example) serve as structural elements in plant cell walls and animal exoskeletons © 2008, YCMOU. All Rights Reserved.7

8. School of Science and Technology, Online Counseling Resource… Polysaccharides-3  Like oligosaccharides, they may be linear or branched.  Important polysaccharides are starch, glycogen (animal starch), cellulose, and chitin.  Starch and glycogen are similar energy- storage molecules found in plants and animals, respectively.  Both are made of glucose molecules that are bonded in the same manner; however, glycogen has a higher degree of branching compared to starch. © 2008, YCMOU. All Rights Reserved.8

9. School of Science and Technology, Online Counseling Resource… Polysaccharide-4  Unlike proteins, polysaccharides generally do not have definite molecular weights.  This difference is a consequence of the mechanisms of assembly of the two types of polymers.  For polysaccharide synthesis there is no template; rather, the program for polysaccharide synthesis is intrinsic to the enzymes that catalyze the polymerization of the monomeric units, and there is no specific stopping point in the synthetic process. © 2008, YCMOU. All Rights Reserved.9

10. School of Science and Technology, Online Counseling Resource… Starch  Starch contains two types of glucose polymer, amylose and amylopectin.  The former consists of long, unbranched chains of D- glucose residues connected by (1n4) linkages.  Such chains vary in molecular weight from a few thousand to more than a million.  Amylopectin also has a high molecular weight (up to 100 million) but unlike amylose is highly branched.  The glycosidic linkages joining successive glucose residues in amylopectin chains are (1n4); the branchpoints (occurring every 24 to 30 residues) are (1n6) linkages. © 2008, YCMOU. All Rights Reserved.10

11. School of Science and Technology, Online Counseling Resource… Glycogen-1  Glycogen is the main storage polysaccharide of animal cells.  Like amylopectin, glycogen is a polymer of (1n4)-linked subunits of glucose, with (1n6)- linked branches, but glycogen is more extensively branched (on average, every 8 to 12 residues) and more compact than starch.  Glycogen is especially abundant in the liver, where it may constitute as much as 7% of the wet weight; it is also present in skeletal muscle. © 2008, YCMOU. All Rights Reserved.11

12. School of Science and Technology, Online Counseling Resource… Glycogen-2  Because each branch in glycogen ends with a nonreducing sugar unit, a glycogen molecule has as many nonreducing ends as it has branches, but only one reducing end.  When glycogen is used as an energy source, glucose units are removed one at a time from the nonreducing ends.  Degradative enzymes that act only at nonreducing ends can work simultaneously on the many branches, speeding the conversion of the polymer to monosaccharides. © 2008, YCMOU. All Rights Reserved.12

13. School of Science and Technology, Online Counseling Resource… Cellulose-1  Cellulose is also made of glucose, but the individual glucose units are linked differently, resulting in a long, fibrous structure that is not soluble in water.  Cellulose is the main structural component of most plant and some protozoan and bacterial cell walls.  Wood is largely cellulose, and paper is an almost-pure sheet of cellulose prepared from wood.  Cellulose constitutes much of the mass of wood, and cotton is almost pure cellulose. © 2008, YCMOU. All Rights Reserved.13

14. School of Science and Technology, Online Counseling Resource… Cellulose-2  Cellulose, a fibrous, tough, water-insoluble substance, is found in the cell walls of plants, particularly in stalks, stems, trunks, and all the woody portions of the plant body.  Like amylose and the main chains of amylopectin and glycogen, the cellulosemolecule is a linear, unbranched homopolysaccharide, consisting of 10,000 to 15,000 D-glucose units.  But there is a very important difference: in cellulose the glucose residues have the ß configuration whereas in amylose, amylopectin, and glycogen the glucose is in the alpha configuration. © 2008, YCMOU. All Rights Reserved.14

15. School of Science and Technology, Online Counseling Resource… Cellulose-3 © 2008, YCMOU. All Rights Reserved.15

16. School of Science and Technology, Online Counseling Resource… Cellulose-4  The glucose residues in cellulose are linked by (1n4) glycosidic bonds, in contrast to the (1n4) bonds of amylose, starch, and glycogen.  This difference gives cellulose and amylose very different structures and physical properties.  Glycogen and starch ingested in the diet are hydrolyzed by -amylases, enzymes in saliva and intestinal secretions that break (1n4) glycosidic bonds between glucose units.  Most animals cannot use cellulose as a fuel source, because they lack an enzyme to hydrolyze the (1n4) linkages. © 2008, YCMOU. All Rights Reserved.16

17. School of Science and Technology, Online Counseling Resource… Cellulose-5  Some 1015 kg of cellulose is synthesized and degraded on Earth each year.  It is an unbranched polymer of glucose residues joined by b-1,4 linkages.  The b configuration allows cellulose to form very long, straight chains.  Fibrils are formed by parallel chains that interact with one another through hydrogen bonds.  The a-1,4 linkages in glycogen and starch produce a very different molecular architecture from that of cellulose. © 2008, YCMOU. All Rights Reserved.17

18. School of Science and Technology, Online Counseling Resource… Cellulose-6  A hollow helix is formed instead of a straight chain.  These differing consequences of the a and b linkages are biologically important.  The straight chain formed by b linkages is optimal for the construction of fibers having a high tensile strength.  In contrast, the open helix formed by a linkages is well suited to forming an accessible store of sugar.  Mammals lack cellulases and therefore cannot digest wood and vegetable fibers. © 2008, YCMOU. All Rights Reserved.18

19. School of Science and Technology, Online Counseling Resource… Cellulose-7  Termites readily digest cellulose(and therefore wood), but only because their intestinal tract harbors symbiotic microorganism, Trichonympha,that secretes cellulase, which hydrolyzes the(1n4) linkages.  Wood-rot fungi and bacteria also produce cellulase. © 2008, YCMOU. All Rights Reserved.19

20. School of Science and Technology, Online Counseling Resource… Chitin-1  Chitin is a linear homopolysaccharide composed of N-acetylglucosamine residues in linkage.  The only chemical difference from cellulose is the replacement of the hydroxyl group at C-2 with an acetylated amino group.  Chitin forms extended fibers similar to those of cellulose, and like cellulose cannot be digested by vertebrates.  Chitin is the principal component of the hard exoskeletons of nearly a million species of arthropods—insects, lobsters, and crabs. © 2008, YCMOU. All Rights Reserved.20

21. School of Science and Technology, Online Counseling Resource… Chitin-2  Chitin is the second most abundant polysaccharide,next to cellulose, in nature.  Chitin is similar to cellulose, but its sugar subunits are a modified form of glucose called N-acetyl glucosamine.  Chitin is the main structural component of fungal cell walls and of animal exoskeletons, such as the shells of insects and crustaceans. © 2008, YCMOU. All Rights Reserved.21

22. School of Science and Technology, Online Counseling Resource… Structures of Polysaccharides © 2008, YCMOU. All Rights Reserved.22

23. School of Science and Technology, Online Counseling Resource… What You Learn…  Polysaccharides are formed of long chains of sugars, most commonly glucose.  Polysaccharides, also called glycans.  Homopolysaccharides contain only a single type of monomer.  Heteropolysaccharides contain two or more different kinds of monomers.  Starch contains amylose and amylopectin.  Glycogen is a polymer of (1n4)-linked subunits of glucose, with (1n6)-linked branches.  In cellulose the glucose residues have the ß configuration  Chitin is a linear homopolysaccharide composed of N- acetylglucosamine residues in linkage. 23© 2008, YCMOU. All Rights Reserved.

24. School of Science and Technology, Online Counseling Resource… Critical Thinking Questions 1.What are polysaccharide and its different types? 2. Why chitin digestion is difficult? 3.Is it possible for mammals to digest cellulose? 4.Write a short note on starch and glycogen. © 2008, YCMOU. All Rights Reserved.24

25. School of Science and Technology, Online Counseling Resource… Hints For Critical Thinking Questions 1.Long chains of sugars, homopolysaccharides and heteropolysaccharides. 2.Due to presence of N-acetylglucosamine residues in linkage. 3.1-6 linkage and Mammals lack cellulasesh 4.Homopolysaccharide of glucose with 1-4 and 1-6 linkage and difference in branching pattern. © 2008, YCMOU. All Rights Reserved.25

26. School of Science and Technology, Online Counseling Resource… Study Tips:1  Book1 Title: Molecular Cell Biology Author: Harvey Lodish, David Baltimore Publisher:Publishers: W. H. Freeman and Company  Book2 Title: Principles of Biochemistry Author: AlbertL Lehninger Publisher:CBS Publishers & Distributors

27. School of Science and Technology, Online Counseling Resource… Study Tips:2  Book3 Title: Biochemistry Author: Lubert stryer Publishers: Freeman International  Book4 Title: Biochemistry Author: Keshav Trehan Publishers: Wiley Eastern

28. School of Science and Technology, Online Counseling Resource… Study Tips www.en.wikipedia.org Microsoft Encarta Encyclopedia http://en.wikipedia.org/wiki/ Wikipedia the free encyclopedia

29. School of Science and Technology, Online Counseling Resource… End of the Presentation Thank You! 29© 2008, YCMOU. All Rights Reserved.