Carbohydrates

Carbohydrates

1. are polyhydroxy aldehyde or polyhydroxy ketones

2. Monosaccharide

   • contain on sugar units
   • according to the number of carbon atoms
     • trioses (3C)
       • Glyceraldehyde
       • dihydroxyacetone
     • tetroses (4C)
       • Erythrose
       • Erythrulose
     • pentoses (5C)
       • ribose
       • ribulose
     • hexoses (6C)
       • glucose
       • fructose
       • galactose
       • mannoses
   • according to the type of carbonyl group
     • aldoses which contains aldehyde group
     • ketoses which contains ketone group
   • Aldoses
     • D-glyceraldehyde
     • L-glyceraldehyde
     • Erythrose
     • Ribose
     • Xylose
     • Galactose
     • Mannose
     • Glucose
   • ketoses
     • dihydroxyacetone
     • Erythrulose
     • Ribulose
     • Xylulose
     • Fructose
   • properties
     • all monosaccharides are reducing due to the presence of free aldehyde group in aldoses and ketol group in ketoses
     • all monosaccharide except dihydroxyacetone contain at least one asymmetric carbon atom which is attached to four different groups or atoms
       • importance of presence of asymmetric carbon atom
         • optical isomer
           • number of isomer= 2^number of asymmetric carbon atom
           • L and D sugars
             • to examine the position of OH attached to carbon atom just above the last one
               • L= left
               • D=right
           • it includes
             • enantiomers:
               • L and d ( sugar and its mirror image)
             • epimers
               • are sugars that differ in the group arrangement around single asymmetric carbon atom
                 • Glucose and mannose as regard to C2
                 • Glucose and galactose as regard to C4
         • Optical activity
           • the ability of the compound to rotate the plane polarized light (ppl) to either
             • Right
               • the compound is called dextrorotatory (d)(+0
                 • D-glocose --> dextrose
             • Left
               • The compound is called leavorotatory (l)(-)
                 • D-fructose --> levulose
             • plane polarized light
               • the light which propagates in only one plane
             • Ordinary light
               • the light which vibrates in all planes
     • ring structure: all hexoses and pentoses can be present in cyclic or ring structure. this ring sturcture starts from C1 in aldoses and C2 in ketoses and ends in C4, C5,C6
       • furanose form
         • C1 --C4
         • C 2-- C5
       • pyranose form
         • C1 -- C5
         • C2 -- C6
       • 2 forms present in the ring structure
         • alpha
           • right
         • beta
           • left
         • called anomers
       • glucose isomers
         • enantiomers
           • L and D isomers
         • epimers
           • with galactose at C4 and mannose at C2
         • furanose and pyranose
         • anomers: alpha and beta
         • aldoses and ketoses isomers: glucose and fructose
   • Derivative
     • deoxyribose
       • the deoxyribose enters DNA structure
     • sugar alcohol
       • glycerol and ribitol which is present in riboflavin (vitamin B2)
     • Sugar acid
       • Aldonic acid
         • first C in aldoses
           • CHO --> COOH
             • glucose --> gluconic acid
       • Uronic acid
         • last C
           • CH2OH --> COOH
             • Glucose --> glocuronic acid
     • amino sugar
       • remove OH at C2 and add NH2
         • Glocosamine
         • galactosamine
         • mannosamine
           • GAG formation glycoprotein, ganglioside formation

3. Disaccharide

   • contain two sugar units
   • reducing
     • Maltose (malt sugar)
       • it is present during starch hydrolysis by amylase
       • formed of
         • 2 alpha d-glucose
       • bonded by
         • Alpha 1,4 glocosidic bond
       • it is reducing due to the presence of free carbonyl group
       • by maltase
         • gives 2 glucose units
     • Lactose (milk sugar)
       • it is present in milk
       • formed of
         • alpha d-glucose
         • beta d- galactose
       • bonded by
         • beta 1,4 galactosidic bond
       • by lactase
         • glucose
         • galactose
       • it is reducing due to the presence of free carbonyl group
   • Non-reducing
     • sucrose (sugar cane)
       • present in the sugar cane
       • it is non reducing due to the absence of the carbonyl group
       • formed of
         • alpha d-glucose
         • beta d-fructose
       • bonded by
         • alpha 1,2 glucosidic bond
       • by sucrase
         • glucose
         • fructose

4. polysaccharide

   • contains more than 10 sugar units
   • Homopolysaccharide
     • by hydrolysis give one type of sugar
     • glucosane
       • starch
         • it is the storage form of carbohydrate in plants present in granes and tubers
         • it is formed of alpha d-glucose units
         • starch has two types of granules
           • amylose
             • inner part
             • 15-20%
             • non-branched
             • alpha 1,4 glucosidic bond
             • with Iodine --> blue color
           • amylopectin
             • outer part
             • branched (24-30 glucose)
             • alpha 1,4 glucosidic bond and alpha 1,6 bond
             • with iodine --> red color
             • 80-85%
       • glycogen
         • the storage form of carbohydrate in animals present in the liver and muscles
         • it is similar to amylopectin but the branches are more numerous and shorter (12-14 glucose)
       • dextrin
         • formed during starch hydrolysis by amylase
         • amylo
         • erythro
         • achrodextrin
       • cellulose
         • present in the walls of plant cells
         • it is water insoluble consists of beta d-glucose and linked by beta 1,4 glucosidic bond
         • it is linear
         • it is not digested due to the absence of the enzyme which acts on the P linkage
         • it increases the bulk of the food which leads to the increase of the intestinal motility so it prevents constipation
     • fructosane
       • inulin
         • present in the root of plants
         • measures GFR
   • heteropolysaccharide
     • by hydrolysis gives more than one type of sugar
     • glycosaminoglycan GAG
       • Sulphate free
         • hyaluronic acid
           • (d-glucouronica + N-acetyl glucosamine)
       • sulphate containing
         • chrondroitin sulphate
         • keratan sulphate
         • dermatan sulphate
         • heparan sulphate
         • heparin sulphate
       • function of GAG
         • chrondoitin sulphate present in the cartilage, bones, ligaments, and tendons
         • dermatan present in the sclera and kermatan present in the cornea
           • heparin is an anti-coagulant, present in the mast cell
             • 1) activation of antithrombin
             • 2) binds fact IX, XI
             • main constituent of extracellular matrix
               • the are polyanionice so attracts Na, K attracts water which leads to lubricating function
                 • heparan plays an important role in the cell interaction

5. olygosaccharide

   • contains 3-10 sugar units