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Nomenclature of carbohydrates lecture biochemistry notees
organic- bio chemistry (CHEM153L)
Xavier University - Ateneo de Cagayan
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THIS MATERIAL IS OWNED BY THE CHEMISTRY DEPT OF 1
C H E M
133 L
B I O C H E M I S T R Y (Laboratory)
Drill 1
Nomenclature of Carbohydrates
Carbohydrates are organic compounds containing many -OH groups (polyhydroxy), and aldehydes or ketones functional groups. Carbohydrates are produced by the process of photosynthesis in which six carbon sugars or hexoses are produced using energy of sunlight, green pigment chlorophyll, CO 2 , and H 2 O by green plants. The general formula of carbohydrates is CnH 2 nOn or Cn(H 2 O)n (hydrates of C) where n= number of atoms.
Simple Classification of Carbohydrates
Monosaccharides. They consist of one sugar containing 3,4,5,6 and 7 carbon atoms and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose (dextrose), fructose (levulose), galactose, xylose, and ribose.
Disaccharides. A sugar (a carbohydrate) composed of two monosaccharides.
Oligosaccharide. An oligosaccharide is a saccharide polymer containing a small number (typically 3-10 monosaccharides
Polysaccharides. Are relatively complex carbohydrates. They are polymers made up of many monosaccharides joined by glycosidic bonds. They are insoluble in water and have no sweet taste.
Monosaccharide structures and types Aldoses: Aldehyde sugars are called aldoses. Ketoses : Ketone sugars are called ketoses.
THIS MATERIAL IS OWNED BY THE CHEMISTRY DEPT OF 2
Drawing Sugar Molecules
Fischer projection represents linear structure of carbohydrates. Shown below is an example of a monosaccharide in Fischer projection.
Haworth projection shows how cyclic forms of carbohydrates are written. It may be an ᾳ- and β- form. The normal form of most sugars is in a cyclic hemiacetal form shown as a Haworth projection.
Sugars are classified according to their structures : according to number of carbon atoms in the sugar and number of sugar units/molecule in a polymer formed by the glycosidic bonds.
Number for carbon atoms Triose sugar units containing three carbon atoms Tetroses sugar units containing four carbon atoms Pentoses sugar units containing five carbon atoms Hexoses sugar units containing six carbon atoms
C H E M
133 L
B I O C H E M I S T R Y (Laboratory)
THIS MATERIAL IS OWNED BY THE CHEMISTRY DEPT OF 4
Drawing/Naming Sugar Molecules: HAWORTH PROJECTION
The Haworth projection is a way around this limitation that does not require you to try to convey the complete 3D image of the molecule. Sugars in Haworth projection can be classified according to the "ring size" ( five - furanoses or six - pyranoses) which they assume in solution. Sugar with fewer than five carbons cannot form a stable ring.
Rules for converting a Fischer structure to a Haworth structure. 1. draw either a pyranose or a furanose ring depending on the sugar. 2. attach "flagpole" carbon above the ring and number the carbons. 3. attach -OH and -H groups using the conventions below: -OH to right -OH down (below ring) -OH to left -OH up (above ring) 4. write name indicating (ᾳ or β anomer) + common name sugar + (replacing suffix -ose) with furanose or pyranose
Anomeric carbon - the new chiral center created when the sugar ring is formed. Anomers - the two new sugar stereoisomers created by ring closure.
C H E M
133 L
B I O C H E M I S T R Y (Laboratory)
THIS MATERIAL IS OWNED BY THE CHEMISTRY DEPT OF 5
B I O C H E M I S T R Y (Laboratory)
Glycoside formation
Disaccharides are two monosaccharides connected by a bridging O atom called a glycosidic bond. Glycosidic bond is a covalent bond between a hemiacetal or hemiketal and an alcohol. Glycoside- compound formed when a sugar in the cyclic form is bonded to an alcohol through a glycosidic bond to another sugar molecule as shown below. The glycosidic linkage is also designated a or β, depending upon whether the conformation at the anomeric carbon is up or down.
Naming Disaccharides Disaccharides which can be regarded as formed by reaction of the two glycosidic (anomeric) hydroxy groups with one another are named, systematically, as glycosyl glycosides.
Name of disaccharides include (ᾳ or β anomer) + common name sugar + (replacing suffix -ose) with furanosyl or pyranosyl-Glycosidic bonds- (ᾳ or β anomer) + common name sugar + (replacing suffix -ose) with furanose or pyranose. In simple terms monossacharide name (syffix yl) – glycosidic linkage
- monossacharide name
C H E M
133 L
- β-D-glucopyranose
THIS MATERIAL IS OWNED BY THE CHEMISTRY DEPT OF 7
C H E M
133 L
B I O C H E M I S T R Y (Laboratory)
Nomenclature of carbohydrates lecture biochemistry notees
Course: organic- bio chemistry (CHEM153L)
University: Xavier University - Ateneo de Cagayan
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