Carbohydrates and Monosaccharides Overview

Carbohydrates

• Function: Provides fast energy for the body, acts as building material and structural support
• Occur in multiple forms: monosaccharide, disaccharide, or polysaccharide
• Consist of C, H, and O atoms typically in a 1:2:1 ratio - has a general formula of (CH2O)n
• Form ring structures in aqueous solutions

Monosaccharides

• Monomer of carbohydrates
• Simple sugars, 1 ring (3-7 carbons)
• Classified by number of carbons
• Major sources of fuel
• Carbon skeleton serves as raw material for the production of other macromolecules
• Functional Groups: OH – hydroxyl

Monosaccharides (important structures)

• Know the structures of glucose, galactose, and fructose
• Be able to link any two of them together to form a disaccharide

Monosaccharides (isomers)

• Glucose, galactose, and fructose are isomers (same formula but different structures) of each other
• Each individual monosaccharide also has multiple different isomers such as α-glucose and β-glucose

Disaccharides

• Two monosaccharides are covalently bonded together by a glycosidic linkage
• Formed by a condensation (dehydration synthesis) reaction
• Water is removed from two hydroxyl groups

Condensation (Dehydration Synthesis) Reaction

• Note: that the glycosidic linkage is made between two hydroxyl functional groups!

Disaccharide examples

• α-glucose + α-glucose = maltose
• α-glucose + fructose = sucrose
• β-glucose + galactose = lactose

Polysaccharides

• Several hundred to thousands of monosaccharides bonded together
• Examples: glycogen, starch, cellulose, chitin
• Function: energy storage or structural molecules

Storage Polysaccharides: Glycogen (Animal)

• Short-term energy storage
• Depleted in one day unless storage is replenished by consumption of food
• Chains of α-glucose molecules
• Highly branched
• Glycogen is hydrolyzed (broken apart into glucose monomers) when blood sugar drops

Storage Polysaccharides: Starch (Plant)

• Short-term energy storage
• Long chains of α-glucose molecules
• Amylose is a type of simple starch that is unbranched (20-30% of the starch, hard to digest – insoluble in water)
• Amylopectin is a complex starch that is branched (70% of the starch, soluble, easy to degrade – has many enzyme attachment points)

Structural Polysaccharides: Chitin

• Exoskeleton of insects and crustaceans
• Cell wall of fungi
• β-glucose monomers contain an amine group

Structural Polysaccharides: Cellulose (Plant)

• Major component of cell walls
• Cannot be digested by humans (we lack the enzyme)
• Consists of β-glucose polymers bonded by beta 1-4 glycosidic linkages

This quiz covers the essential aspects of carbohydrates, focusing on their function, structure, and the different types of monosaccharides. Test your knowledge of simple sugars, their isomers, and how they link to form disaccharides. Understand the fundamental roles carbohydrates play in providing energy and supporting macromolecule production.