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Chemistry of carbohydrates and their structure
The document discusses carbohydrates and their classification. It notes that carbohydrates include monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides can be further classified as aldoses or ketoses depending on whether they have an aldehyde or ketone functional group. Common monosaccharides include trioses, tetroses, pentoses, and hexoses. Disaccharides are formed from the condensation of two monosaccharide units and include maltose, sucrose, and lactose. Polysaccharides are formed from the condensation of many monosaccharide units and can be homopolysaccharides or heteropolysaccharides.
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Chemistry of carbohydrates and their structure
- 2. Aldehyde orKetone derivatives of polyhydroxy alcohols. General formula (CH2O)n
- 3. Most abundantbio molecules. Main source of energy (4 kcal/gm) . Absolutely required for RBCs’ & brain cells. Storage form of energy i.e. starch & glycogen. Required for oxidation of fats. Excess CHO are converted into fats. Glyco protein & Glyco lipids are components of cell membrane. Structural basis of many organisms. Used as drugs i.e. antibiotics & cardiac Glycosides.
- 4. Monosaccharides Disaccharides Oligosaccharides Polysaccharides Derived carbohydrates
- 5. Simplest sugars,cant be hydrolyzed into simpler molecules. Further classified as, Aldoses Ketoses
- 6. NAME GENERAL FORMULA ALDOSES KETOSES TRIOSESC3H6O3 GLYCER- - ALDEHYDE DIHYDROXY- - ACETONE TETROSES C4H8O4 ERYTHROSE ERYTHROLUS E PENTOSES C5H10O5 RIBOSE RIBULOSE HEXOSES C6H12O6 GLUCOSE FRUCTOSE HEPTOSES C7H14O7 SEDOHEPTOL USE NONOSES C9H18O9 NEURAMINIC- -ACID
- 7. Condensation productsof 2 monosaccharide units. MALTOSE (D Glucose + D Glucose) SUCROSE (D Glucose + D Fructose) LACTOSE (D Glucose + D Galactose)
- 8. Condensation productsof 3-10 mono saccharide units,most of them are not digested by human enzymes. α DEXTRINS MALTO TRIOSE
- 9. Condensation productsof > 10 mono saccharide units. HOMO POLY SACCHARIDES HETRO POLY SACCHARIDES
- 10. HOMO POLYSACCHARIDES Haveonly one type of mono saccharide units. STARCH GLYCOGEN CELLULOSE INULIN DEXTRIN DEXTRAN CHITIN
- 11. MUCO POLY SACCHARIDES Also known as Glycosaminoglycan. Hyaluronic Acid,Chondriotin sulfate, Heparin sulfate, Keratin sulfate, Dermatin sulfate, Blood group substances. GLYCO CONGUGATES Proteo glycans Glyco lipids Glyco proteins
- 12. Reduction productsi.e. Polyols (glycerol) Oxidation products i.e. sugar acids Deoxy sugars i.e. DNA
- 13. TRIOSES Glyceraldehyde &Dihydroxy acetone. 1 Intermediates of glycolysis. 2 Precursor of Glycerol TETROSES Erythrose-4-PO4 1 Intermediate of HMP shunt.
- 17. L- Fucose Deoxy Glucose D- Ribose L- Arabinose D- xylose
- 20. Glucose Fructose Galactose Mannose
- 22. Colorless, crystallinesolids , sweet taste, water soluble compounds. Aldoses Ketoses Poly Hydroxy alcohols i.e. having (OH-) groups Depending upon the no. of (OH-) groups, they contain one or more centre of Asymmetry, which affects their optical & biological activity.
- 23. Dihydroxy acetone(ketotriose) is an exception, (does not have any asymmetric carbon). Glyceraldehyde (aldotriose) is called as the “REFERENCE SUGAR”. Carbonyl carbon Asymmetric carbon
- 24. ISOMERISM INMONOSACCHARIDES 1. Stereo isomerism 2. Enantiomers 3. D & L isomers 4. Optical isomers 5. Aldose-Ketose isomers 6. Anomers 7. Epimers 8. Pyranose & Furanose isomers
- 25. 2 ormore Monosaccharides having same formula, but differing from each other in structural configuration i.e. spatial arrangement of H or OH atoms in their structure.
- 26. 4 differentgroups attached to the same carbon . Parent compound (reference molecule) is Glyceraldehyde (1 asymmetric C).
- 28. In generala molecule with n chiral center can have 2n stereo isomers. Glyceraldehyde 21 Glucose 2 4
- 29. ENANTIOME RS These are mirror imagesof each other. They form D & L isomers. All mono saccharides can be considered to be derived from Glyceraldehyde.
- 31. The configurationof H & OH groups at the second Carbon atom of Glyceraldehyde forms D & L sugars. Penultimate carbon atom is the reference carbon for naming D & L mirror images.
- 32. Non superimposable complete mirror images, differ in configuration at every chiral center. In D form OH group is on the RIGHT , while in L form OH group is on the LEFT of the chiral carbon. D & L isomers differ from each other by orientation around PENULTIMATE CARBON (C -5 in case of Glucose molecule) ,farthest from the carbonyl(C= O)carbon. Human body can metabolize D-sugars only. Naturally occuring sugars are D-sugars except L-Arabinose .
- 34. Presence ofasymmetric C atom confers optical activity to the carbohydrates. When a beam of plane polarized light is passed through a carbohydrate solution It will rotate the light either to right DEXTRO ROTATORY(+) to left LEVO ROTATORY (-)
- 35. The directionof rotation of plane polarized light is independent of the stereo-chemistry of sugar. Sugar may be designated as, D(-) ,D(+) or L(-) ,L(+) Naturally occuring form of Fructose is D but it is levo rotatory. i.e. ( D-) Glucose is D sugar, but dextro rotatory i.e. (D+)
- 36. Plane polarizedlight does not rotate to right or left, if Compound does not possess plane of asymmetry. Equal amounts of dextro or levo isomers are present RECEMIC MIXTURE. Meso compounds having asymmetric carbon but due to internal compensation i.e. Meso tartaric acid.
- 37. Sugars thatdiffer only in the configuration around one Carbon atom (other than reference carbon).
- 41. Cyclic structuresare formed by the reaction between an ALDEHYDE/KETONE group and a HYDROXYL group in a monosaccharide with 5 or more carbon atoms. Cyclic structure is thermodynamically favored and accounts for many properties of mono -saccharides
- 42. The openchain form (FISCHER PROJECTION) is found in < 0.1% of the molecules in an aqueous solution. An intra molecular reaction in which one of the OH group of the sugar is added to the Aldehyde/ Ketone group of the same molecule ---- forms a cyclic structure. The cyclic (ring) structure is called ----------- HAWORTH PROJECTION. The carbonyl carbon(C-1 of Aldose /C-2 OF KETOSE) in ring structure is called ANOMERIC CARBON
- 49. Condensation betweenKetone group and a OH group forms the hemi Ketal linkage. Condensation between the Aldehyde/Keto group is in 1:1. As a result of these linkages ANOMERIC CARBON gives an additional asymmetric carbon. Depending upon the configuration, OH group are found above or below the ring. OH group on the right in Fischer projection appear under the ring in Haworth projection ,while those on the left are above the ring.
- 50. OH groupat C-5 / C-6 reacts with the Keto group at C-2, forming a FURANOSE/PYRANOSE cyclic structure having a hemi Ketal linkage. D-Fructose readily forms the Furanose ring. Common anomer of Fructose is the β - D Fructose.
- 52. In Aldohexosesthe OH group at C-5 reacts with the c=o group and forms a six member ring---PYRAN RING . Sugars having this ring are called PYRANOSES. If the OH group at C-4 reacts, a five member ring--- FURAN RING is formed & Sugars are called FURANOSES. OH group to the right is below the plane----α Oh group to the left is above the plane of symmetry--- β
- 55. Anomeric carbonby giving an additional chiral carbon makes the total isomers 25. (32) Anomeric carbon gives 2 stereo isomers i.e. α & β ANOMERS . α & β forms are not Enantiomers. They differ only in respect to configuration around Anomeric carbon. They are present only in cyclic form, & do not show the Aldehyde group normally present in Glucose. Ring structure is also called AMYLENE OXIDE .
- 56. In Glucosesolution ,2/3 of sugar exist as β form,& 1/3 as α form. Inter conversion of α & β forms is called MUTA ROTATION . In the solution there is opening of Hemiacetal ring to form traces of Aldehyde sugar & then Re condensation to the cyclic form.
- 59. When planepolarized light is passed through a Molar solution of D- Glucose, Its specific rotation keeps on changing α- D Glucose in the solution shows --+112˳ while β- Glucose shows ---- +19˳. After a certain period of time two forms reach at an end point---- +19˳. Mutarotation leads to an equilibrium between α & β forms in which 62% of the molecules are present in the β form , while 38% in the α form. a
- 60. α & βAnomers can be obtained in pure forms. It is possible to determine the sugar content of different beverages.