Carbohydrates come in simple and complex forms, from single sugar units to long chains. They're classified by their structure, like having an aldehyde or ketone group, and named based on carbon count and functional groups.

Stereochemistry plays a big role in carbohydrates, with many having multiple possible 3D arrangements. This affects how they behave and interact in biological systems, influencing their function in our bodies and nature.

Classification of Carbohydrates

Simple vs complex carbohydrates

• Simple carbohydrates consist of monosaccharides (glucose, fructose) and disaccharides (sucrose, lactose) with 1-2 sugar units
  • Monosaccharides are single sugar units that cannot be hydrolyzed into smaller carbohydrates
  • Disaccharides are formed by two monosaccharides joined by a glycosidic bond and can be hydrolyzed into two monosaccharides
• Complex carbohydrates include oligosaccharides and polysaccharides with 3 or more sugar units linked by glycosidic bonds
  • Oligosaccharides contain 3-10 monosaccharides and can be hydrolyzed into individual monosaccharides
  • Polysaccharides are formed by many monosaccharides (>10) and can be hydrolyzed into numerous monosaccharides (starch, cellulose)

Aldoses and ketoses classification

• Aldoses contain an aldehyde group ($-CHO$) at the end of the carbon chain with the general formula $C_n(H_2O)_n$
  • Examples include glucose, galactose, and ribose
  • Many aldoses are reducing sugars due to their free aldehyde group
• Ketoses contain a ketone group ($C=O$) within the carbon chain with the general formula $C_n(H_2O)_n$
  • Examples include fructose, ribulose, and sorbose

Monosaccharide naming conventions

• Carbon count is indicated by the prefix:
  • Triose: 3-carbon monosaccharide
  • Tetrose: 4-carbon monosaccharide
  • Pentose: 5-carbon monosaccharide (ribose)
  • Hexose: 6-carbon monosaccharide (glucose, fructose)
  • Heptose: 7-carbon monosaccharide
• Functional group characteristics are indicated by the root word:
  • Aldehyde group ($-CHO$) indicates an aldose (aldotriose, aldohexose)
  • Ketone group ($C=O$) indicates a ketose (ketopentose, ketohexose)
• Combining the prefix and root identifies the monosaccharide:
  • Glucose is an aldohexose (6-carbon aldose)
  • Fructose is a ketohexose (6-carbon ketose)
  • Ribose is an aldopentose (5-carbon aldose)

Stereochemistry of Carbohydrates

• Chirality is a key feature of most carbohydrates, resulting in multiple stereoisomers
• Stereoisomers have the same molecular formula but different spatial arrangements of atoms
• Anomers are stereoisomers that differ in configuration at the anomeric carbon (C1 in aldoses)
• Mutarotation is the interconversion between α and β anomers in solution