Carbohydrates

Introduction to Carbohydrates

Carbohydrates are essential biomolecules that play critical roles in cell structure, cellular identity, and energy storage. Their functions are determined by their chemical structure and how their monomers are linked together.

• Monosaccharides: Simple sugars, also called "one-sugar" monomers.

• Oligosaccharides: Short chains of monosaccharide units, "few-sugars" small polymers.

• Polysaccharides: Long chains of monosaccharide units, "many-sugars" large polymers.

Structure of Monosaccharides

Monosaccharides are the simplest carbohydrates and serve as building blocks for more complex carbohydrates. They have a general formula and specific structural features.

• General Formula: Most monosaccharides have the formula (e.g., glucose is ).

• Minimum Structure: At least 3 carbon atoms, 1 carbonyl group (C=O), and 2 hydroxyl groups (-OH).

• Classification by Carbonyl Group Position:

  • Aldose: Carbonyl group at the end of the carbon chain.

  • Ketose: Carbonyl group within the carbon chain.

Naming Monosaccharides by Carbon Number

Monosaccharides are named according to the number of carbon atoms they contain. This affects their chemical properties and biological roles.

• Triose: 3 carbons (e.g., Dihydroxyacetone)

• Tetrose: 4 carbons

• Pentose: 5 carbons

• Hexose: 6 carbons (e.g., Glucose)

Isomerism in Monosaccharides

Monosaccharides with the same number and type of atoms can differ in the arrangement of their atoms, forming isomers.

• Structural Isomers: Differ in the location of the carbonyl group (aldose vs. ketose).

• Stereoisomers: Differ in the spatial arrangement of atoms (e.g., D-glucose vs. L-glucose).

Examples

• Glucose: A hexose (6C) aldose, primary energy source in cells.

• Dihydroxyacetone: A triose (3C) ketose, involved in metabolic pathways.

Table: Classification of Monosaccharides

Additional info:

• Monosaccharides can exist in linear or ring forms, with the ring form being predominant in aqueous solutions.

• Monosaccharides are the foundation for oligosaccharides and polysaccharides, which are formed by glycosidic linkages.