Carbohydrates

• Carbohydrates


  - most direct source of chemical energy
• Ways to classify carbs

  - number of sugars moieties

  - carbons in each sugar

  - functional groups

  - stereochemistry of sugar
• Monosaccharides


  - most basic unit

  - three carbons

  - can become cyclic
• Trioses


  - 3 carbons in a monosaccharides
• Tetrose


  Carbohydrate with 4 carbon
• Pentose


  Carbohydrate with 5 carbon
• Hexose


  Carbohydrate with 6 carbon
• Aldose


  Carbohydrate with aldehyde group as most oxidized functional group
• Ketose


  Carbohydrate with ketone group as most oxidized functional group
• Aldohexose


  - carbohydrate with 6 C and a aldehyde functional group
• Glyeraldehyde


  - reflects basic structure of a monosaccharide

  - aldose

  - three parts

  1. O = C - H

  2. H - C - OH

  3. CH2OH
• Aldehyde carbon


  - always be C1

  - participates in glycosidic linkages
• Glyosyl resiudes


  - sugars that are substiuents via this linkage
• Dihydroxyacetone


  - simplest ketose

  - Carbonyl group = most oxidized

  - lowest number for carbonyl C is C2

  - can participate in glycosidic linkage

  HO-CH2-C=O-CH2-OH
• D Fructose


  - 6 carbons

  - ketose (2nd carbon)

  CH2OH

  C=O

  OH-C-H

  H-C-OH

  H-C-OH

  CH2OH
• D Glucose


  - 6 carbons

  - aldose

  CHO

  H-C-OH

  HO-C-H

  H-C-OH

  H-C-OH

  CH2OH
• D Galactaose


  - 6 carbons

  - aldose

  CHO

  H-C-OH

  HO-C-H

  HO-C-H

  H-C-OH

  CH2OH
• D Mannose


  - 6 Carbons

  - aldose

  CHO

  HO-C-H

  HO-C-H

  H-C-OH

  H-C-OH

  CH2OH
• Optical isomers


  - aka steroisomers

  - same chemical formula

  - differ in spatial arrangement
• Enantiomers


  - isomers

  - non identical

  - non superimposable

  - mirror images
• Chiral carbon


  - C with 4 dif things attached to it

  - no internal planes of symmetry

  - has enantiomers
• Absolute configuration


  - the specific 3D attachment of groups to a chiral C
• D and L system

  - replaces R and S

  - D does not always mean R

  - D is positive rotation

  - L is negative rotation

  - is found experimentally
• Stereoisomer equation


  number of stereoisomers = 2^n

  - n = number of chiral molecules
• Diastereomer


  - same family

  - not identical

  - not mirror
• Epimers


  - Diastereomer that differ in configuration at exactly one chiral center
• Hemiacetals


  - cyclic form of aldoses
• Hemiketals


  - cyclic form of ketoses
• Cyclic molecules stable in solution

  - pyranose (6)

  - furanose (5)
• Anomeric carbon


  - when forming cyclic ring, the carbonyl carbon becomes chiral = anomeric carbon

  - C1 carbon and C5 interact
• Ring formation from cyclization of sugar


  - α

  - β

  - differ at the anomeric carbon

  - termed as anomers
• α - anomer


  - OH group of C1 is trans to CH2OH
• β - anomer


  - OH group of C1 is cis to CH2OH
• Haworth projection


  - 3D conformation of cyclic structures

  - Right of Fisher project point down
• Mutaroation


  - C1 and C2 substiuents can rotate freely = form either α or β anomer

  - occurs more rapidly when catalyzed with acid or base

  - results in mixture of α and β at equilibrium concentration
• Equilibrium concentrations for glucose α and β

  36% α (more hindrance = less favored)

  64% β
• Hemiacetal rings in water

  - spontaneously cycle between open and close
• Oxidation of carbohydrates


  yields energy for body
• Aldonic acids


  oxidized aldose long chains
• Reducing agent


  - aldose

  - any hemiacetal ring