Chemistry of Carbohydrates, Amino Sugars and Mucopolysaccharides MCQs

The respiratory quotient of fats is 0.7 RQ of carbohydrates is 1.0 RQ of proteins is 0.81 Reference: Harper's illustrated biochemistry 32 nd edition page 138

Ans. A. Sucrose Disaccharides Sugar Units Linkage Trehalose (Sugar of αDGlucose + α1 ------- α1 linkage insect hemolymph, αDGlucose yeast and fungi) Sucrose (Cane Sugar) αDGlucose α1 ------- β2 +β DFructose linkage

A) When sugars are different from one another, in configuration with regard to a single carbon atom, along with the reference carbon atom, they are called epimers : This statement is true and defines the concept of epimers. B) Mannose is epimer of Glucose at 2nd Carbon : This statement is true. Mannose and glucose differ in their configuration at the second carbon atom. C) Galactose is epimer of glucose at 4th Carbon : This statement is also true. Galactose and glucose differ in their configuration at the fourth carbon atom. So, the only statement that is not true is option D , which states that Mannose and Galactose are not epimers. In fact, they are epimers of glucose, but at different carbon atoms (Mannose at the second carbon and Galactose at the fourth carbon). Reference: Harper's 32 nd edition, Page 154

General test for all Carbohydrates Molisch test Test for Reducing Substances Benedict's Test Test to differentiate Monosaccharides and Disaccharides Barfoed's Test Moore's test Fehling's Test Test to differentiate Aldoses and Ketoses Seliwanoff's Test Rapid furfural Test Foulger's Test Test to detect Deoxy Sugar Feulgen Staining Test for Pentoses Bial's Test Test for Galactose Mucic Acid Test. Reference: DM Vasudevan, S Sreekumari 8 edition, page 95, 96

Ans. is `b' i.e., Heparan sulphate [Ref Dinesh puri Yale p. 31, 32] Proteoglycans are made up of core protein, core trisaccharide and glycosaminoglycans. Proteoglycans = Glycosaminoglycans + Core trisaccharide + Core protein. Glycosaminoglycans (mucopolysaccharides) are made up of repeating diasaccharide units. Each diasaccharide unit contains?

This molecule is present on many cell surfaces as a proteoglycan and is extracellular. It contains GlcN with fewer N -sulfates than heparin, and, unlike heparin, its predominant uronic acid is GlcUA. Heparan sulfate is associated with the plasma membrane of cells, with their core proteins actually spanning that membrane. In this, they may act as receptors and may also participate in the mediation of the cell growth and cell to cell communication. The attachment of cells to their substratum in culture is mediated at least in part by heparan sulfate. This proteoglycan is also found in the basement membrane of the kidney along with type IV collagen and laminin, where it plays a major role in determining the charge selectiveness of glomerular filtration. Reference: Harper's 32 nd edition, Page no. 637, 638

Option C: Heparan Sulfate is present in a proteoglycan found on many extracellular cell surfaces. It contains GlcN with fewer N-sulfates than heparin and unlike heparin, its predominant uronic acid is GlcUA. Heparan sulfates are associated with the plasma membrane of cells, with their core proteins actually spanning that membrane. Heparan sulfate is also found in the basement membrane of the kidney along with type IV collagen and laminin, where it plays a major role in determining the charge selectiveness of glomerular filtration.

Hyaluronic acid consists of an unbranched chain of repeating disaccharide units containing GlcUA and GlcNAc. It is present in bacteria and is found in the ECM of nearly all animal tissues, but is especially high in concentration in highly hydrated types such as skin and umbilical cord, and in bone, cartilage, joints (synovial fluid) and in vitreous humor in the eye, as well as in embryonic tissues. It is thought to play an important role in permitting cell migration during morphogenesis and wound repair. Its ability to attract water into the ECM triggers loosening of the matrix, aiding this process. Reference: Harper's 32 nd edition, Page no. 637