exp 5 - carbs

• how is monosaccharides classified

  number of C and functional group
• stoichiometric formula, where n is the number of carbons in the molecule (the ratio of C:H:O is 1:2:1)

  (CH2O)n
• polyhydroxy aldehydes or ketones

  carbohydrates
• In monosaccharides, the number of carbons usually ranges

  3 to 7
• form when two monosaccharides undergo a dehydration reaction


  condensation reaction or dehydration synthesis
• A long chain of monosaccharides linked by glycosidic bonds

  polysaccharides
• Monosaccharides May be classified depending on:

  • the number of C in the sugar • the functional group
• Glucose and fructose are _______ _____ at RT but are highly soluble in ___

  crystalline solids; H2O
• isomeric monosaccharides.


  Glucose, galactose, and fructose
• In an aqueous solution, 5- and 6-C monosaccharides exist as an ________ _______ of three forms: between linear and 2 ring forms (α or β anomers).

  equilibrium mixture
• also form rings, although they form 5-membered rings 


  Fructose and ribose
• serves as a reducing agent due to its free aldehyde or ketone functional groups in its structure.

  Reducing Sugar
• grain sugar


  maltose
• table sugar


  sucrose
• milk sugar


  lactose
• General Reactions of Carbohydrates

  1.MolischTest 2.AnthroneTest 3.IodineTest
• Specific Reactions of Carbohydrates 


  Mucic Acid Test, Benedict, Barfoed, Bial’s-Orcinol, Seliwanoff, Fehling
• 1. Starch from Potato
  2. Glycogen from Chicken Liver

  Isolation of Carbohydrates
• identify an unknown monosaccharide or disaccharide.


  Specific Reactions of Carbohydrates
• 7 sugar sol.


  20% standard sugar solutions of: (1) xylose (XYL) ; (2) fructose (FRU) ;

  (3) glucose (GLU); (4) galactose (GAL); (5) lactose (LAC) ; (6) maltose (MAL) ; and (7) sucrose (SUC)
• The starch that comes from potatoes is a

  polysaccharide and is composed of

  amylose and 70-80% .


  amylopectin
• Starch is in water and rapidly

  settles at the bottom and can be collected

  by decanting the supernatant.

  insoluble
• Glycogen is in water due to the

  presence of hydroxyl groups on the

  glucose molecules.

  soluble
• The is an excellent source of glycogen.

  liver
• A colometric test that determines if the given analyte

  contains carbohydrates or not.

  Molisch Test
• Positive result: Formation of a purple/purplish-red ring at the

  contact point of the H SO & the analyte.

  Negative result: Absence of a ring

  Molisch
• 1 g of α-naphthol (C H OH) dissolved in 100

  mL of 95% ethanol (C H OH)


  molisch reagent
• Principle

  Carbohydrates are present.

  Sulfuric acid = a dehydration reaction

  Formation of an aldehyde or a furfural derivative

  Condensation reaction with two phenol-type molecules

  Molisch
• Purple/reddish-purple complex


  molisch
• Positive result: Blue-green solution

  Negative result: Yellow solution

  anthrone
• result: Anthrone-Furfural complex (blue-green complex)


  anthrone
• 2g of Anthrone (10-keto-9, 10-dihydroanthracene)added in 1 liter of concentrated (H2SO4)

  Anthrone
• Lugol‘s iodine Reagent: 5% elemental iodine, 10% potassium iodide, and distilled water


  iodine test
• Positive result: Presence of blue-black solution.

  Negative result: Formation of all other colors (brown/yellow).

  iodine test
• detection of polysaccharides


  iodine test
• Starch consists of amylose and amylopectin, the _______ is responsible for the reaction of iodine.

  amylose
• + result of molisch, anthrone, iodine

  m: purple/purplish-red ring

  a: blue-green sol.

  i: blue-black/purple sol.
• Starch is present

  Addition of potassium iodine = reversible reaction of the

  iodine ion

  Binding of I to the polysaccharide’s coiled shape

  iodine test
• identify galactose, including sugars

  containing galactose like lactose.

  mucic acid test
• Positive result: Presence of crystals forming at the tube‘s base

  mucic acid test