Carbohydrates

• Building blocks 


  Determine the structure and function of biomolecules
• Carbohydrates (monosaccharides)


  joined by glycosidic bond
• Proteins (Amino Acids) 


  joined by Peptide bonds
• Nucleic Acids (nucleotides) 


  joined by phosphodiester bonds
• Lipids (fatty acids and glycerol )

  components tell how they are linked together
• Carbohydrates 


  Most abundant biomolecules on earth .
• carbohydrates are polyhydroxy aldehydes or ketones, that yielded such compounds in hydrolysis
• Three major classes of carbohydrates

  • monosaccharides
  • olihosaccharides
  • polysaccharides
• Monosaccharides


  simple sugar, consist of a single polyhydroxy aldehyde or ketone.
• Most abundant monosaccharide in nature is six carbon sugar d-glucose, or dextrose
• all monosaccharides except dihydroxyacetone contain one or more asymmetrical chiral carbons atoms thus occur in optically active isomer forms
• monosaccharides 


  molecule with n chiral centers can have 2 to the nth power strieoisomers
• Fischer convention

  absolute configuration D,L system

  prefix L - rotation to the left

  Prefix D - rotation to the right
• epimers


  differ only in the configuration around one carbon
• cyclic structures 


  known as Haworth Structures

  formation of rind structures is a result between the reaction of ketone and alcohol to form derivatives hemiacetals or meniketals
• six-membered ring compounds are called pyranose because they resemble pyran a six-member compound
• five membered rings called hexos beacouse they resemble a ring compound furan called furanoses
• anomers


  isomeric forms of monosaccharides that differ only in their configuration about hemeiketal carbon atom
• hemiacetal carbonyl is also called anomeric carbon
• Mutarotation


  reaction of sugar in water (Monosaccharides
• Dehydration


  reaction of monosaccharides in concentrated mineral acids
• Dilute mineral acids


  Monosaccharides are stable in dilute mineral acids
• isomerization 


  dilute alkali or base
• Fragmentation 


  concentrated alkali or base
• monosaccharides are reducing agents
• only CHO group of monosaccharides can be oxidized to COOH by mild oxidizing agent
• reducing sugars


  sugars capable of reducing ferric or cupric ion
• Fehling reaction 


  qualitative test for the presence of reducing sugar
• glucose oxidase


  sensitive method fir measuring blood sugar glucose enzyme
• string oxidizing agents 


  oxidize both CHO and 1degres OH to COOH
• alduronic acid 


  Specific oxidoreductase oxidizes only the 1 degree OH NOT the CHO
• mild reducing agents converts CHO to CH2OH
• ribitol 


  component of flavin coenzymes
• glycerol and cyclic polyhydroxy alcohol myoinositol


  important lipid components
• xylitol 


  sweetener used for sugarless gum
• string RA


  sugar is converted to hydrocarbon
• glycosides


  it is from when condensation of anomeric group of a sugar with an alcohol
• glycosidic bond


  bond connecting the anomeric carbon to the alcohol oxygen
• N glycosidic bond


  form between the anomeric carbon and amine
• reducing sugar


  saccharides nearing anomeric carbon that have not formed glycosides