carbohydrates

• 3 functions of carbohydrates

  major energy sources, play key role in processes on surfaces of cells: cell-cell interactions and immune recognition, and structural component
• Polyhydroxy aldehydes, polyhydroxy ketones or compounds that can be hydrolyzed to them

  carbohydrates
• cellulose, chitin, starch, and glycogen


  polysaccharides
• sugars linked by glycosidic bonds

  oligosaccharides
• general formula of glucose

  C6H12O6
• single carbonyl group and two or more OH groups, cannot be hydrolyzed

  monosaccharides
• simplest monosaccharide with 3 carbon atoms

  triose
• mirror-image, nonsuperimposable stereoisomers, d and l

  enantiomers
• molecules differ from each other only in their configuration

  stereoisomers (optical isomers)
• dextro, most common esp in glucose


  right
• levo


  left
• 2D representations of the stereochemistry of 3D molecules

  Fischer projections
• Most highly oxidized carbon is written at the top


  C-1
• OH is on the right

  D configuration
• OH is on the left

  L configuration
• D sugars differ in configuration at only 1 carbon

  Epimers
• Why do cyclic sugar exists?

  Stability
• Interaction between functional groups on C-1 and C-5, to form hemiacetal in aldohexoses


  Hemiacetal
• compound that is formed by the reaction of an aldehyde with an alcohol

  Hemiacetal
• Interaction between C-2 and C-5 results in ______ formation in ketohexoses

  Hemiketal
• compound formed by the rxn of a ketone with an alcohol


  hemiaketal
• hemiacetal and hemiaketal, the carbonyl carbon becomes a chiral center called

  anomeric carbon
• open-chain form

  fischer projection
• cyclic form

  haworth projection
• cyclic sugar with a 5 membered ring, very nearly planar rings


  furanose
• cyclic sugar with a 6 membered ring, chair conformation ring solution

  pyranose
• cis


  B
• trans


  a
• mutarotation cyclization reaction is _______

  reversible
• in solution, the cyclic form interconverts with the ____________ form

  open-chain
• cyclic form


  a and B anomer
• open-chain form


  D and L sugar
• all are reducing sugars

  monosaccharides
• aldehyde groups can be oxidized to give the _______ group

  carboxyl
• aldoses are _________ sugars that contain a free carbonyl group and can react with an oxidizing agent

  reducing
• also reducing sugars because they can isomerize to aldoses

  ketoses
• linkages responsible for the bonding of monosaccharides to form oligo and poly

  glycosidic linkage
• 3 disaccharides


  sucrose, lactose, maltose
• common table sugar, not a reducing sugar, monosaccharide units a-D-glucose and B-D-fructose, glycosidic linkage a,B(1->2)

  sucrose
• made up of B-D-galactose and D-glucose, glycosidic linkage B(1->4)

  lactose