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CARBOHYDRATES

CARBOHYDRATES. LECTURE OUTLINE. By the end of the lecture, the student should know: The Importance of carbohydrates. The Definition of Carbohydrates. The Classification of Carbohydrates. The Difference between various Isomers. CARBOHYDRATE: IMPORTANCE. Most Abundant Class of Biomolecules.

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CARBOHYDRATES

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  1. CARBOHYDRATES

  2. LECTURE OUTLINE By the end of the lecture, the student should know: • The Importance of carbohydrates. • The Definition of Carbohydrates. • The Classification of Carbohydrates. • The Difference between various Isomers..

  3. CARBOHYDRATE: IMPORTANCE • Most Abundant Class of Biomolecules. • An Important Macronutrient. • Performs important physiological functions in the body. • Associated with Pathological Conditions (Diabetes Mellitus, Lactose Intolerance).

  4. DEFINING CARBOHYDRATES Carbohydrates or Saccharides(Greek Sakcharon meaning "Sugar") • Organic compounds composed of Carbon, Hydrogen and oxygen. • Many Carbohydrates also contain Nitrogen and other elements.

  5. Carbohydrates derive their name from a Misleading Concept'Hydrates of Carbon’ • Hydrogen and Oxygen in Carbohydrates were found to be present in the same proportion as in water. (2:1).(E.g. Glucose C6H12O6 or C6 (H2O)6). • It is due to this fact that compounds derived their name “Carbon Hydrate”.

  6. GLUCOSE H-C=O  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH

  7. This term is not a perfect derivation as many carbohydrates do not have the same proportion as water. Example: DEOXYRIBOSE (C5H10O4) H-C=O  H-C-H  H-C-OH  H-C-OH  CH2OH

  8. CHEMICAL DEFINITION OF CARBOHYDRATES • Polyhydroxyl: Having more than one hydroxyl group. (-OH) • Functional Group: It is a specific group of atoms or bonds which are part of a larger hydrocarbon chain.(Provide a specific chemical behaviour).

  9. For carbohydrates, the functional group is the carbonyl group which may be either Aldehyde Group (H-C=O) Or Keto Group (C=O)

  10. H-C=O  H-C-OH  OH-C-H  H-C-OH  CH2OH CH2OH  C=O  OH-C-H  H-C-OH  CH2OH WHAT IS SIMILAR & DIFFERENTIN THESE TWO STRUCTURES? More than one hydroxyl group in both

  11. H-C=O  H-C-OH  OH-C-H  H-C-OH  CH2OH CH2OH  C=O  OH-C-H  H-C-OH  CH2OH WHAT IS COMMON & DIFFERENTIN THESE TWO STRUCTURES? Carbonyl Group in both But?

  12. H-C=O  H-C-OH  OH-C-H  H-C-OH  CH2OH CH2OH  C=O  OH-C-H  H-C-OH  CH2OH What is common & differentin these two Structures? Aldehyde in 1 and Ketone in 2

  13. Carbohydrates arePolyhydroxy Alcoholswith Carbonyl groupsWhich May Either BeAldehyde (H-C=O) orKeto (C=O) Groups.

  14. H - C CH OH 2 ½ O ½ C H - C - OH ½ ½ OH - C - H OH - C - H ½ ½ H - C - OH H - C - OH ½ ½ H - C - OH H - C - OH ½ ½ CH OH CH OH 2 2 Can you Visualize Either AldehydeOrKetone Group In This Polyhydroxy Alcohol?

  15. H - C CH OH 2 ½ O ½ C H - C - OH ½ ½ OH - C - H OH - C - H ½ ½ H - C - OH H - C - OH ½ ½ H - C - OH H - C - OH ½ ½ CH OH CH OH 2 2 No! But Hydrolysis of This Compound Yields Two Compounds with Aldehyde Or Ketone Groups HOH

  16. No! But Hydrolysis of This Compound Yields Two Compounds with Aldehyde Or Ketone Groups H - C CH OH =O HOH 2 ½ O ½ O= C H - C - OH ½ ½ OH - C - H OH - C - H ½ ½ H - C - OH H - C - OH ½ ½ H - C - OH H - C - OH ½ ½ CH OH CH OH 2 2

  17. Many Polyhydroxy Alcohols may Not have an active Aldehyde or Ketone Group But they May YieldThem On Hydrolysis. They Are Also Designated as Carbohydrates.

  18. THEREFORE, THE COMPLETE DEFINITION OF CARBOHDRATES IS: CARBOHYDRATES ARE POLYHYDROXYL ALCOHOLS WITH POTENTIALLY ACTIVE CARBONY GROUPS WHICH MAY BE EITHER AN ALDEHYDE OR KETONE GROUP. THEY ALSO CONTAIN THOSE COMPOUNDS, WHICH YIELD THEM ON HYDROLYSIS.

  19. Classification of carbohydrates Carbohydrates are mainly classified into four different groups: • Monosachharides • Disaccharides • Oligosaccharides • Polysaccharides

  20. MONOSACCHARIDES • Monosaccharides are those carbohydrates which Cannot be Hydrolyzed further into more simple carbohydrates. • Thus, they are the Simplest form of Carbohydrates. • Familiar examples are: Glucose, Fructose, Ribose & Galactose.

  21. Monosaccharides are further classified on the basis of: • Aldehyde or Ketone Group: • Aldomonosaccharides (Aldoses). • Ketomonosaccharides (Ketoses). • Carbon Chain Length. • Trioses. • Tetroses. • Pentoses. • Hexoses. • Heptoses.

  22. CARBONYL GROUP H-C=O  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH CH2OH  C=O  OH-C-H  H-C-OH  H-C-OH  CH2OH GLUCOSE FRUCTOSE-->

  23. CARBON CHAIN H-C=O  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH H-C=O  OH-C-H  H-C-OH  H-C-OH  CH2OH GLUCOSE ARABINOSE-->

  24. EXAMPLES OF MONOSACCHARIDES

  25. glyceraldehyde

  26. GLYCERALDEHYDE IS THE SIMPLEST MONOSACCHARIDE(PARTICULARLY ALDOSES) • IT CANNOT BE HYDROLYZED FURTHER. • IT IS THE SMALLEST POSSIBLE STRUCTURE THAT IS A CARBOHYDRATE CANNOT HAVE LESS THAN 3 CARBON ATOMS. • GENERAL FORMULA OF MONOSACCHARIDE: (C•H2O)N (WHERE N IS ANY NUMBER OF THREE OR GREATER)

  27. isomerism • Isomers are basically molecules that have the same chemical formula but they differ in their chemical structures. • Asymmetric Carbon is an important determinant of Isomerism. • Asymmetric Carbon is that Carbon which is attached with four different groups.

  28. Anomeric Carbon Epimeric Carbons Penultimate Carbon Terminal Alcohol Carbon Straight Chain Structure of Typical Monosaccharide (Glucose)

  29. OH H The assignment of D or L is made according to the orientation of the Penultimate Carbon If the Hydroxyl Group is on the right the molecule is a D sugar, Otherwise It is an L sugar. L-Sugar : D-Sugar

  30. D and L isomerism produce mirror images

  31. epimerism • Isomers which differ from each other only with regard to oh group on a single asymmetric carbon atom.

  32. Optical isomers • When a beam of polarized light is passed through sugars, they will be rotated either towards right or left. • Right Rotation (dextrorotatory) E.g. D- Glucose • Left Rotation (levorotatory) E.g. D-Fructose

  33. Monosaccharide Derivatives of Biological Importance • Oxidation Products (Sugar Acids) • Reduction Products (Sugar Alcohols). • Amino Sugars. • Sugar Phosphates.

  34. Oxidation Products (Sugar Acids) • When oxidized under proper conditions, Aldoses may form three types of acids (Sugar Acids): • Uronic Acids. • Aldonic acids. • Saccharic Acids. • Type of sugar Acid produced depends on which carbon is oxidized.

  35. Uronic Acid H-C=O  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH Oxidation Of Aldose At Primary Alcohol (Terminal Carbon) COOH

  36. H-C=O  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH Oxidation Of Aldose At Carbonyl Carbon (Aldehyde Group) Aldonic Acid COOH

  37. H-C=O  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH Oxidation Of Aldose At Both Aldehyde & Terminal Carbons Saccharic Acid COOH COOH

  38. Sugar Glucose ------------- Mannose ------------- Galactose ------------- Uronic Acids Glucuronic acid, Iduronic acid ---------------------- Mannuronic acid ---------------------- Galacturonic acid ------------------------ Examples of Aldoses with their Corresponding Uronic Acids are:

  39. Sugar Glucose ------------- Mannose ------------- Galactose ------------- Aldonic Acids Gluconic acid ---------------------- Mannonic acid ---------------------- Galactonic acid ------------------------ Examples of Aldoses with their Corresponding Aldonic Acids are:

  40. Amino Sugar: H-C=O  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH • Substitution of Amino Group for a Hydroxyl Group of a Sugar Results in the Formation of an Amino Sugar. • The Amino Group is attached to Carbon 2. NH2

  41. Common Examples of Amino Sugars (Aminosaccharides) • Galactosamine • Glucosamine

  42. Sugar Alcohols; Reduction Products • Sugar Alcohols are obtained by reduction of Monosaccharides (Both Aldoses and Ketoses) and disaccharides. • Sugar alcohols, also known as Polyols, Polyhydric Alcohols, or Polyalcohols.

  43. H- C=O + H2  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH Glucose CH2OH  H-C-OH  OH-C-H  H-C-OH  H-C-OH  CH2OH Sorbitol Sugar Alcohols are the Hydrogenated forms of the Aldoses or Ketoses

  44. Glyceraldehyde & Dihydroxyacetone Glucose Mannose Fructose Galactose Ribose Erythrose Xylose Lactose Maltose Glycerol Sorbitol (Glucitol) Mannitol Sorbitol & Mannitol Dulcitol Ribitol Erythritol Xylitol Lactitol Maltitol Sugars with their Corresponding Alcohols

  45. Sugar Phosphates • Phosphate Esters formed by various Monosaccharides are of Great Importance in Metabolic Reactions. • Sugar phosphates of biological importance. • Ribose and Deoxyribose in Nucleic Acids are Phosphate Esters of these monosaccharides. • Phosphates of Glucose, Fructose and Glyceraldehyde etc. are important intermediate compounds in carbohydrate metabolism of almost all the cells.

  46. Disaccharides • Two Joined Monosaccharides. • Sucrose: Glucose + Fructose • Maltose: Glucose + Glucose • Lactose: Glucose + Galactose

  47. Oligosaccharides Composed Of: • Three To Ten Monosaccharide Units. • E.g. Fructooligosaccharides 

  48. Polysaccharides • Larger Than Ten Monosaccharide Units. • Can Reach Many Thousands Of Units. • Homopolysaccharides. • Heteropolysaccharides.

  49. Homopolysaccharides • Similar Types of Monosaccharide Units. • Starch • Glycogen • Cellulose

  50. Heteropolysaccharides • Different Types of Monosaccharide Units. • Mucopolysaccharides (Glycosaminoglycans that contain galactose and amine sugars) • Agar (Contains various sugars like Glucose, Galactose)

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