carbs

• Biochemistry


  The study of the chemistry of biomolecules and living organisms
• In organic chemistry, we organized our study of carbon-containing molecules by functional group (alcohol, alkene, ketone, carboxylic acid, etc.)
• Important biological molecules


  • Carbohydrates
  • Lipids
  • Proteins and enzymes
  • Nucleic acids
• Carbohydrates


  Polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis
• Classes of carbohydrates


  • Monosaccharides
  • Disaccharides
  • Oligosaccharides
  • Polysaccharides
• Monosaccharides


  Contain a single polyhydroxy aldehyde or ketone unit (e.g., glucose, fructose)
• Disaccharides


  Consist of two monosaccharide units linked together by a covalent bond (e.g., sucrose)
• Oligosaccharides


  Contain from 3 to 10 monosaccharide units (e.g., raffinose)
• Polysaccharides


  Contain very long chains of hundreds or thousands of monosaccharide units, which may be either in straight or branched chains (e.g., cellulose, glycogen, starch)
• Chiral


  Molecules that have the same relationship to each other that your left and right hands have when reflected in a mirror
• Chiral carbon


  Any carbon atom which is connected to four different groups
• If any of the two groups on the carbon are the same, the carbon atom cannot be chiral
• 2n rule


  When a molecule has more than one chiral carbon, each carbon can possibly be arranged in either the right-hand or left-hand form, thus if there are n chiral carbons, there are 2n possible stereoisomers

  
• Fischer projection


  A convenient way to represent mirror images in two dimensions
• Optical activity


  The ability of a substance to rotate the plane of polarized light
• Levorotatory (-)


  A substance that rotates polarized light to the left
• Dextrorotatory (+)


  A substance that rotates polarized light to the right
• Classification of monosaccharides


  • Triose
  • Tetrose
  • Pentose
  • Hexose
• Aldose


  Monosaccharides with an aldehyde group
• Ketose


  Monosaccharides with a ketone group
• Most monosaccharides have a sweet taste, with fructose being the sweetest at 73% sweeter than sucrose
• Monosaccharides are extremely soluble in water due to the presence of large numbers of OH groups
• Relative sweetness of sugars

  • Lactose
  • Galactose
  • Maltose
  • Xylose
  • Glucose
  • Sucrose
  • Invert sugar
  • Fructose
• 1. ribulose


  Ketopentoses
• 22 = 4
• The Family of D-ketoses

  • D-Sorbose
  • D-Tagatose
  • D-Psicose
  • D-Fructose
• (L-forms not shown)
• Ketohexoses


  • D-Sorbose
  • D-Tagatose
  • D-Psicose
  • D-Fructose
• 23 = 8
• Physical Properties of Monosaccharides

  • Most monosaccharides have a sweet taste (fructose is sweetest; 73% sweeter than sucrose)
  • They are solids at room temperature
  • They are extremely soluble in water
• Glucose can dissolve in minute amounts of water to make a syrup (1 g / 1 ml H2O)
• Relative Sweetness of Sugars

  • Lactose
  • Galactose
  • Maltose
  • Xylose
  • Glucose
  • Sucrose
  • Invert sugar
  • Fructose
• Monosaccharides


  Do not usually exist in solution in their "open-chain" forms: an alcohol group can add into the carbonyl group in the same molecule to form a pyranose ring containing a stable cyclic hemiacetal or hemiketal
• Glucose Anomers


  In the pyranose form of glucose, carbon-1 is chiral, and thus two stereoisomers are possible: one in which the OH group points down (-hydroxy group) and one in which the OH group points up (-hydroxy group)
• Fructose Anomers


  Fructose closes on itself to form a furanose ring
• Drawing Furanose and Pyranose Rings

  • Monosaccharides are often represented using the Haworth structures
  • The remaining OH groups on the ring point up or down depending on the identity of the sugar

  
• Anomers


  • ribose
  • galactose
• Reducing Sugars


  Aldehydes and ketones that have an OH group on the carbon next to the carbonyl group react with a basic solution of Cu2+ (Benedict's reagent) to form a red-orange precipitate of copper(I) oxide (Cu2O)
• Phosphate Esters


  • Phosphate esters can form at the 6-carbon of aldohexoses and aldoketoses
  • Phosphate esters of monosaccharides are found in the sugar-phosphate backbone of DNA and RNA, in ATP, and as intermediates in the metabolism of carbohydrates in the body
• Glycoside Formation


  • The hemiacetal and hemiketal forms of monosaccharides can react with alcohols to form acetal and ketal structures called glycosides
  • The new carbon-oxygen bond is called the glycosidic linkage