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Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides

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Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Paper : 04 Metabolism of carbohydrates Module : 01 Prelude: Carbohydrates (Part-A) –Mono & Oligosaccharides Principal Investigator Dr.S.K.Khare,Professor IIT Delhi. Paper Coordinator Dr. Ramesh Kothari,Professor UGC-CAS Department of Biosciences Saurashtra University, Rajkot-5, Gujarat-INDIA Dr. S. P. SinghProfessor Content Reviewer UGC-CAS Department of Biosciences Saurashtra University, Rajkot-5, Gujarat-INDIA Dr. Ramesh Kothari,Professor UGC-CAS Department of Biosciences Content Writer Saurashtra University, Rajkot-5, Gujarat-INDIA 1 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Description of Module Subject Name Biochemistry Paper Name 04 Metabolism of Carbohydrates Module Name/Title 01 Prelude: Carbohydrates (Part-A)- Mono & Oligosaccharides Dr. Vijaya Khader Dr. MC Varadaraj 2 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides PRELUDE-CARBOHYDRATES- (Monosaccharide’s and Oligosaccharides) Objectives 1. Introduction and the function of Functions of carbohydrates 2. To understand classification of carbohydrates 3. To study the characteristics of carbohydrates 4. To understand the properties of mono- and di- saccharides: 3 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Introduction Carbohydrates are one of the three major macronutrients in our diet representing a wide group of substances which include the sugars, starches, glycogen, gums and celluloses. Carbohydrates are known as the important energy source for living things. They comes from the process of photosynthesis, an endothermic reaction in which condensation of carbon dioxide takes place and which requires light energy and the pigment chlorophyll. The chemical component of carbohydrates is carbon, hydrogen, and oxygen. Generally, but not always the hydrogen and oxygen in carbohydrates are present in the proportion oftwo hydrogen atoms to one oxygen atom as in H2O, from which fact the term “carbohydrates” was derived The carbohydrates are actually or potentially hydroxy aldehydes or ketones, and in most cases they are polyhydroxy aldehyde or ketones compounds that can be hydrolyzed to them. It also means “hydrate of carbon” Plant biomass is made up of three fourths of carbohydrates but in animal body it is present in small quantities. In animal it is stored in the form of glycogen, sugar and their derivatives All living organism contains derived monosaccharides such as the sugar acids, amino sugars and the deoxysugars Derivatives of the carbohydrates also contain nitrogen, phosphates and sulfur compounds. Carbohydrates can combine with lipid and protein to form glycolipids and glycoproteins. Carbohydrates and their derivatives are present in all animal tissues and tissue fluids, blood and milk. The glucosides are a class of carbohydrates are derivatives which are frequent constituents of plants 4 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides The major components of living matter is formed from carbohydrates, proteins and fats This complex form of carbohydrates is required for the maintenance of cell structure and functions Presence of functional group like alcohol on almost every carbon makes the chemistry of carbohydrates a complex structure Carbohydrate may be exist in either a straight chain or a closed ring structure. The general reaction between the aldehyde and ketone part of the carbohydrates and alcohol groups forms the derivative called hemiacetals and hemiketals leads to the formation of ring structure. The most common basic structure of carbohydrates is closed rings Glucose is an example of a single closed ring carbohydrate Functions of carbohydrates The simplest carbohydrates are initially synthesized in plants by the process of photosynthesiswhich is a series of reactions. Carbohydrate functions as… bio Fuel primary Source of Energy storage food framework in body anticoagulant antigen hormone provide raw material for industry Essential for Fat Oxidation plays role in gastro-intestinal function add flavour to the diet play an important role in molecular recognition 5 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Classification The carbohydrates are sometimes referred to as the saccharides The word saccharides comes from the Greek word sakcharon meaning sugar Those carbohydrates such as glucose and fructose that cannot be hydrolyzed into simpler compounds are called simple sugars or monosaccharides Certain carbohydrates are made of two molecules of monosaccharides such as sucrose, lactose and maltose These carbohydrates are called dissarcharides. Similarly, trisaccharides are composed of three and tetrasaccharides of four monosaccharides molecules All these compound carbohydrates may be readily hydrolyzed into their constituent monosaccharides by heating with dilute acids or by the action of specific enzymes According to the number of C atoms and functional groups in its simplest form of carbohydrates are further classified The suffix –ose indicates the types of sugar. Nomenclature of carbohydrates based on number of carbon atoms 1. Triose= 3 carbon atom(Glyceraldehyde, Dihydroxyacetone 2. Tetrose= 4 carbon atom(Erythrose) 3. Pentose= 5 carbon atom(Ribose, Ribulose, Xylulose) 4. Hexose=6 carbon atom(Glucose, Galactose, Mannose, Fructose) 5. Heptose=7 carbon atom(Sedoheptulose) and so on 6 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Characteristics of carbohydrates Isomerism Isomers are defined as molecule with the same chemical formula and often with the same kinds of chemical bonds between atoms, but in which the atoms are arranged differently i.e. they have different structural formulae. Isomerism can be of two types: Structural isomerism and Stereoisomerism 7 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Monosaccharides Greek, mono=one; sakchron=sugar. Monosaccharides are the simplest sugar formed by the single molecules which furthercannot be hydrolyzed into smaller units. Depending upon the number of carbon arrangement in a unit, mono saccharides are subdivided into aldoses and ketoses. The aldoses and ketoses are represented by the following general formulas. 8 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Study of the chemical and physical properties of many sugar has shown the cyclic forms predominate over open chain structure, both in solution and in the solid state. Alcohol may react with aldehyde and ketone moieties of the carbohydrates to form an unstable compounds called hemiacetals or hemiketals, respectively. This is a reaction between two molecules, i.e., it is intermolecular In glucose the –OH on carbon 5 (C-5) can react intramolecularly with carbonyl group (on C-1) to form a stable, cyclic hemiacetal. The cyclic form of glucose is a six- membered ring; such sugars are called pyranose because they resemble pyran. Fructose forms a five membered ring called furanose as it resembles furan. 9 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides The pyranose and furanose ring structure of sugar proposed by Haworth more accurately represent their actual configuration than do the older projection structures used by Fischer and other workers, though the older ring forms are still used extensively in writing reaction of sugars. The pyranose ring of a six carbon aldose sugar can exist in either a boat or a chair configuration The substituents attached to the ring carbon thatextend parallel to the symmetry are said to be axial (a) whereas those that extend outward from the axis are said to be equatorial (e). 10 Metabolism of Carbohydrates Biochemistry Prelude: Carbohydrates (Part-A)-Mono & Oligosaccharides Stereoisomerism Many of the carbohydrates contain the same number of atoms and the same kinds of groups, yet definitely distinct substances For example, the formula C6H12O6 represents 16 differently simple sugars all processing the structure CH2OH.CHOH.CHOH.CHOH.CHOH.CHO This is due to differently arrangement of the constituent groups of the molecules in space. This phenomenon represents what is called stereoisomerism (space isomerism) and these sugars are stereoisomers. An asymmetric carbon atom is a carbon when it is attached to four different types of atoms or groups When there are several asymmetric carbon atoms in a chain molecule and the end group are not identical, the number of stereoisomers possible is equal to 2n, where n is the number of asymmetric carbon atoms For example glucose contains 4 asymmetric carbon and thus are 24= 16 isomers. The simplest monosaccharides is glyceraldehydes Glyceraldehyde has a single asymmetric carbon atom (the central one) and so two stereoisomers (also called optical isomers) are possible, that is two forms of glyceraldehyde, denoted as D- and L-glyceraldehyde, which are mirror images of each other It has been possible to relate the spatial configuration of sugars, amino acids and many other optically active substances of biological importance to the configuration of the dextro and levo forms of glyceraldehydes Monosaccharides can be named by a system that is based on the number of carbons with the suffix –ose added. There is also a system for numbering the carbons. They 11 Metabolism of Carbohydrates Biochemistry
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