some impor monosaccharide for BS students full notes.pptx

The monosaccharide consists of single unit which contains carbon chain of three to six carbon. They can combine through glycosidic bonds to form larger carbohydrates. The main function of monosaccharide is to produce and store energy. Glucose and fructose are the most available monosaccharide in nature.

1. Notes on

2. 1.Hexoses Hexoses include the following: Glucose Fructose Galactose Mannose These are as described

3. i. D-glucose Also called grape sugar and dextrose. Occur widely in nature (in fruits, sugar cane, sugar beats, dates) Also occur in combination with other monosaccharide forming important disaccharides like sucrose , maltose etc. Combination of large number of glucose units give rise to polysaccharides such as glycogen.

4. Glucose is also commercially obtained by hydrolysis of starch which is a polymer of hundreds or thousand of D-glucose units. Human blood plasma contain normally 70-110 mg glucose/dL in the fasting condition. Under normal condition only traces of glucose can pass through urin. In diabetic patients a large amount of glucose can be found,

5. The term blood sugar is used for blood glucose because glucose represent almost 100% of monosaccharide in blood. On reduction of glucose it form the alcohol sorbitol. On being oxidized in vitro glucose give rise to three types of sugar acids depending on experiments.

6. Glucose can occur in both in pyranose and furanose form. But the former is more stable and predominant.

7. Properties of glucose It is 74% as sweet as sucrose. It is readily fermented by yeast. Utilized by tissues for instant energy.

8. Structure of glucose Physiologically and biomedically , glucose is the most important monosaccharide. The structure of glucose can be represented in the following ways 1 . The straight chain structural formula (Fisher projection ).

9. 2. Cyclic formula (Ring structure or Haworth projection)

10. Monosaccharide in solution is mainly present in ring form. In solution, aldehyde (CHO) or ketone (C=O ) group of monosaccharide react with a hydroxy (OH ) group of the same molecule forming a bond hemiacetal or hemiketal respectively. The aldehyde group of glucose at C-1 reacts with alcohol (OH) group of C-5 or C-4 to form either six membered ring called glucopyranose or five memberedring called glucofuranose, respectively. However , in case of glucose, the six membered glucopyranose is much more stable than the glucofuranose ring. In the case of fructose, the more stable form is fructofuranose. (as mention eariler.)

11. ii.D-Fructose Also known as the fruits sugar. Obtain from Latin word fructus which means fruits. And also called levolose due to levorotation. Occur in honey and in plants kingdom in combination with glucose in sucrose. The polysaccharide used in investigating kidney function yields it on hydrolysis.

12. Animals tissues also contain it in a small amount. Seminal fluid has an appreciable amount of fructose. It serve as source of energy for spermatozoa. Fructose show mutarotation like glucose. The specific rotation of its fresh solution is(-)135.5 degree which falls after some time to (-)92.3 degrees.

13. Fructose can occur in pyranose form having 2 to 6rings as well as in furanose form. When free it occur in pyranose form which is levorotatory. But in sucrose it occur in furanose form which is dextrorotatory. Sweet of all sugars 173% fermented by yeast.

14. iii.galactose Occur as a part of lactose molecule when combine with glucose. Also occur in seed coats of legumes. It is constituents of glycolipids and glycoproteins. It has aldohexoses. It is dextrorotatory. Exhibit mutarotation. 32% as sweet as sucrose.

15. It differ from glucose only in respect to configuration around carbon no 4. The two sugar which differ from each other around one carbon atom are called epimers. So galactose is an epimer of glucose in respect to carbon no 4.

16. D-Mannose It is the part of the molecule of a prosthetic polysaccharide of many glycoproteins. Also present in polysaccharide components of tuberculoproteins. If ingested it is absorbed. Body convert it to glucose. Show similar chemical reaction to glucose. It cannot be differentiated from glucose by osazone test.

17. It differ from glucose only in configuration around carbon no 2 in simple word it is an epimer of glucose in respect to carbon no 2.

18. 2.pentoses These are the monosaccharide containing a chain of five carbon atoms. They occur widely in nature. In plants as well as in animal kingdom. Usually they are the component of polysaccharide of plants and animals kingdom. Ribose is a constituent of a ribonucleic acid of the cell and of many important substance found in cell like ATP,GTP,CTP.UTP.NAD+,NADP+,FMN,FAD

19. And coenzymes. All these components are of great importance for all living organisms.

20. Properties of pentose's May be aldoses or ketosis. Posses strong reducing properties. Form osazone crystals with penylhydrazine. With acids they are converted into furfurals. Can’t be fermented by yeast.

21. Physiological role Ribose and ribulose as phosphate are intermediates in pentose phosphate pathway of glucose metabolism. L-xylulose is an intermediate in uronic acid pathway of glucose metabolism. D-lyxose is found in heart muscles as a component of lyxoflavin. D-arabinose and D-xylose are found in glycoproteins Important for herbivorous animals but not in human.

22. 3.Deoxysugars These represent sugars in which oxygen of OH group has been removed leaving behind H. The most important deoxy sugar is pentose sugar termed as 2-deoxy-D-ribose usually called 2-deoxyribose. It i s the constituent of deoxyribonucleic acid(DNA). This give most of sugar reaction but does not form osazone.

23. It is unstable. In tissues its presence can be shown by Feulgens reaction which involves the reaction of 2-deoxyribose with Schiffs reagents. Deoxy hexoses also occur in nature e.g L-fucose in milk and blood. Another deoxyhexose 2-deoxyglucose is used in research. It is taken by tissues like glucose but unlike glucose it is not metabolized.