Carbohydrates and Their Types

Carbohydrates

• Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen.
• They are categorized into monosaccharides, oligosaccharides, and polysaccharides.

Monosaccharides

• Simplest form of carbohydrates, also called simple sugars.
• General formula: Cn(H₂O)n
• Examples: glucose, fructose, galactose
• Building blocks of carbohydrates
• Cannot be broken down further by hydrolysis.

Oligosaccharides

• Formed by linking a few (2-10) monosaccharides.
• Examples: disaccharides like sucrose (table sugar) and lactose (milk sugar).

Polysaccharides

• Large molecules composed of many monosaccharide units.
• Examples: starch, cellulose, glycogen.

Stereoisomers

• Enantiomers: Mirror-image stereoisomers
  • D-glucose and L-glucose are enantiomers.
• Epimers: Sugars that differ in configuration at only one chiral center.
  • D-glucose and D-mannose are C-2 epimers.
  • D-glucose and D-galactose are C-4 epimers.

Cyclization and Anomers

• Monosaccharides with 5 or 6 carbon atoms often form ring structures.
• Cyclization occurs when a carbonyl group reacts with a hydroxyl group on the same molecule.
• This creates a new chiral center (anomeric carbon).
• The resulting ring structure exists in two forms: α-anomer and β-anomer.
• Hemiacetals and hemiketals are more stable than their corresponding open-chain forms.

Haworth Projections

• Two-dimensional representations of the cyclic forms of monosaccharides.

Mutarotation

• Interconversion of α and β anomers.

Chair Conformation of Glucose

• β-D-glucose is more stable than α-D-glucose.
• The equatorial position of the hydroxyl group on C1 in β-forms is more stable than the axial position in α.

Oxidation Reactions

• Oxidation reactions convert aldoses to lactones.
• Tollens' test example of an oxidation reaction.
• A cyclic ester linking the carboxyl group and a sugar alcohol is called a lactone.

Reduction Reactions

• Reduction reactions convert sugars to deoxy sugars or alditols.
• Deoxy sugars: a hydrogen atom replaces a hydroxyl group, examples include L-fucose and D-2-deoxyribose.
• Alditols: carbonyl group reduced to a hydroxyl group, examples include xylitol and sorbitol.

Sugar Esters, Phosphates, and Glycosides

• Sugar esters result from reacting alcohol with an acid.
• Sugar phosphates are sugar esters.
• Glycosides are formed when hemiacetals or hemiketals react with another alcohol
• Full acetals/ketals: complete replacement of both -OH groups with -OR groups.

Explore the fascinating world of carbohydrates, including their classifications into monosaccharides, oligosaccharides, and polysaccharides. This quiz will test your understanding of their structures, examples, and functions, including important concepts like stereoisomers.