CARBOHYDARTE II Done By :Nisreen Moh’d

Polysaccharides Cellulose: the major structural component of plants, especially wood and plant fibers a linear polymer of approximately 2800 D-glucose units per molecule joined by b-1,4-glycosidic bonds fully extended conformation with alternating 180° flips of glucose units extensive intra- and intermolecular hydrogen bonding between chains

Cellulose can’t be digested by humans because their cells don’t have the needed enzymes to break B-1,4 glycosidic linkages

Starch A polymers of a-D-glucose units and used for energy storage in plants, 2 forms amylose: continuous, helical unbranched chains of up to 4000 a-D-glucose units joined by -1,4-glycosidic bonds amylopectin: a highly branched helical polymer consisting of 24-30 units of D-glucose joined by _1,4-glycosidic bonds and branches created by -1,6-glycosidic bonds amylases catalyze hydrolysis of -1,4-glycosidic bonds debranching enzymes catalyze the hydrolysis of

Starch

Starch: storing form of carbs in plants Has Straight & branched chains All monosacharrides are reducing sugar Percentages of carbs in human diet: 60% starch 30% sucrose 10% lactose

Polysaccharides Branching in amylopectin and glycogen The difference between amylopectin and glycogen is no. of branches Glycogen every 10 Amylopectin every 25

Glycogen : storage form of glucose in animals Glycogen is stored in liver & muscles Why glycogen is highly branched ?? -for quick hydrolysis and synthesis Why glycogen has globular form ?? -decreasing the needed space for storage ; if it were in fibers form for example it would take too much space for small amount To hydrolyze 1 gram of glycogen the body need to boil 2.5 gram of water

Polysaccharides Chitin: the major structural component of the exoskeletons of invertebrates, such as insects and crustaceans; also occurs in cell walls of algae, fungi, and yeasts composed of units of N-acetyl--D-glucosamine joined by -1,4-glycosidic bonds

Not soluble in water Similar structure to keratin that is found in hair &nails It is homopolysaccaride or heteropolysaccaride ?? -it is a homopolysaccaried because it consists of the same repeated unit of which is N-acetyl--D-glucosamine

Polysaccharides Bacterial cell walls: prokaryotic cell walls are constructed on the framework of the repeating unit NAM-NAG joined by b-1,4-glycosidic bonds

Bacterial Cell Walls The N-acetyl-D-glucoseamine and N-acetylmuramic acid polysaccharide is in turn cross-linked by small peptides in Staphylococcus aureus, the cross link is a tetrapeptide this tetrapeptide is unusual in that it contains two amino acids of the D-series, namely D-Ala and D-Gln each tetrapeptide is cross linked to an adjacent tetrapeptide by a pentapeptide of five glycine units Peptidoglycan: is the resulted cross linking of polysaccharides by peptides

Bacterial Cell Walls

Bacterial cell wall is heteropolysaccaride consisting of 2 units: NAM & NAG NAM is coming from muramic acid that contains 9 atoms of carbon

Bacterial Cell Walls The Peptidoglycan of a bacterial cell wall Staphylococcus aureus

خريطة مفتاحية NAM جزيء NAGجزيء خمس جزيئات من الحمض الأميني غلايسين مركب رباعي الببتيد أي انه يتكون من اربعة احماض امينية اثنان منهما هما ألانين و غلوتامين NAM جزيء NAGجزيء

Polysaccharides Glycosaminoglycans: polysaccharides based on a repeating disaccharide where one of the monomers is an amino sugar and the other has a negative charge due to acid such as a sulfate or carboxylate group heparin: natural anticoagulant hyaluronic acid: a component of the vitreous humor of the eye and the lubricating fluid of joints chondroitin sulfate and keratan sulfate: components of connective tissue

The repeating unit of heparin

The repeating unit of hyaluronic acid

Chondroitin sulfate The repeating unit of chondroitin sulfate

ANTICOAGULANT >>> مادة تمنع تجلط الدم Remember that NAG is found in : 1))chitin 2))bacterial cell wall 3))hyaluronic acid

Glycoproteins antibodies are glycoproteins Glycoproteins contain carbohydrate units covalently bonded to a polypeptide chain antibodies are glycoproteins carbohydrates play a role as antigenic determinants, the portions of the antigenic molecule that antibodies recognize and to which they bond.

Glycoproteins : بروتينات تحمل جزيئات كاربوهيدرات Carbs that are found in the surface of the cell membrane serve as recognition sites the foreign bodies unit with the carb in the surface of cells which is a sign for the immune system that those cells are abnormal and there is something wrong !After this sign the immune system (WBC’s&macrophages) begins it’s work Autoimmune disease : disability of the body to differ between it’s normal and abnormal cells

Blood Group Substances Membranes of animal plasma cells have large numbers of relatively small carbohydrates bound to them: these membrane-bound carbohydrates act as antigenic determinants among the first antigenic determinants discovered were the blood group substances in the ABO system, individuals are classified according to four blood types: A, B, AB, and O at the cellular level, the biochemical basis for this classification is a group of relatively small membrane-bound carbohydrates

ABO Blood Classification

ABO Blood Classification in type A, the nonreducing end is NAGal in type B it is Gal in type AB, both types are present in Type O, neither of these terminal residues is present

AB : universal receiving O : universal donor O B A AB

End Chapter 16