[MA2] BIOCHELB - Carbohydrates

• Starch is storage unit for solar energy
• Most sugars have formula Cn (H2O)n , “hydrate of carbon.”
• Synthesized by plants using sunlight to

  convert CO2 and H2O to glucose and O2

  Carbohydrates
• can be used as starting materials for the biological synthesis of other types of compounds in the body

  carbohydrates
• simple sugars


  monosaccharides
• can be hydrolyzed to a few

  monosaccharides

  Oligosaccharides
• hydrolyze to many monosaccharide units

  polysaccharides
• Monosaccharides are classified by: 


  aldose or ketose
• it is classified by configuration of chiral carbon farthest from the carbonyl group

  monosaccharides
• aldose


  .

  
• ketose


  .

  
• Consist of 2 monosaccharides bonded together

  disaccharides
• Lactose, sucrose, maltose

  Disaccharides
• Contain glycosidic bond


  Disaccharides
• used to provide protective walls or lubricative coating to cells - cellulose and mucopolysaccharides


  structural polysaccharides
• structural peptidoglycans


  bacterial cell walls
• >10 monosaccharides


  Polysaccharides
• Polysaccharides


  Most are made up of hundreds of monosaccharides bonded together
• type of polysaccharides that is responsible for storage in plants

  starch
• type of polysaccharides that is responsible for storage in animals

  glycogen
• type of polysaccharides that is not used for energy by humans but key for grazing animals

  dietary fiber/cellulose
• amylose


  when the 1-4 condensation of a-D-glucose is repeated many times, you have a polyglucose named _____
• random branches of glucose in the alpha (1-6) glycosidic linkage at a branching point

  amylopectin
• the sugar solution is mixed with alphanaphthol and layered with concentrated H2S04 , forming a violet ring.


  molisch test
• This is a general test for carbohydrates

  molisch test
• seliwanoff test


  involves the action of concentrated HCl and resorcinol on the sugar
• a red color is developed rapidly in the presence of a ketose sugar, such as fructose


  Seliwanoff Test
• reaction is used for the detection of galactose, because it forms insoluble saccharic acid (mucic acid).


  Saccharic acids
• Fehling's solution


  made by adding to solution of CuSO4 a solution containing Rochelle salt and NaOH.
• When a sugar solution containing a free aldehyde or ketone group is boiled with Fehling's solution, the characteristic result in a brick-red precipitate of Cu20.
• contains CuS04 , Na2C03 , and sodium citrate.

  Benedict's Solution
• Benedict's Solution


  Because of its weaker alkalinity it is more sensitive than Fehling's solution.
• made up of cupric acetate to which have been added a few drops of acetic acid.

  Barfoed's Solution
• Barfoed's Solution


  used to distinguish between mono- and disaccharides.
• Nylander's Solution


  contains bismuth subnitrate, potassium hydroxide, and Rochelle salt.
• Nylander's Solution


  On boiling with a solution of a reducing sugar, black metallic bismuth precipitates.
• If the aldehyde group of a simple sugar is reduced, the corresponding polyhydric alcohol is obtained.
• Reactions of Sugars with Phenylhydrazine

  If a solution of reducing sugar is heated with phenylhydrazine, a yellow precipitate is finally obtained (osazone).
• uses copper ions to detect reducing sugars in an acidic solution.

  barfoed
• nylander


  black precipitate to indicate reaction