Monosaccharides: Can participate in redox reactions, being categorized as either reducing or non-reducing sugars.
2. Oxidation of Sugars
Aldehydes: May be oxidized to carboxylic acids.
Example: D-glucose (aldose) can be oxidized to gluconic acid (aldonic acid).
Reducing Sugars: These sugars can react with Benedict's or Tollens' reagents due to their ability to reduce metal ions (Cu²⁺, Ag⁺).
3. Reducing Sugars and Tests
Benedict's Test:
Detects reducing sugars by reducing Cu²⁺ to Cu⁺, forming a colored precipitate.
Tollens' Test:
Silver ion (Ag⁺) is reduced to metallic silver when reacting with reducing sugars.
4. Rearrangement of Sugars
Ketoses: Under basic conditions, ketoses can rearrange to form an aldose (a reducing sugar).
Both aldoses and ketoses react with Benedict's and Tollens' reagents to form aldonic acids.
5. Glycosidic Linkages
Types: Glycosidic linkages can be differentiated as alpha (α) or beta (β) based on the orientation of the anomeric carbon.
Significance: This orientation influences the biological function and digestibility of carbohydrates.
Examples: Maltose has an α(1→4) linkage, while cellulose has a β(1→4) linkage leading to different properties.
6. Polysaccharides
Monomers: Glucose is the monomer unit for common polysaccharides like starch and cellulose.
Structure:
Starch: Consists of amylose (linear) and amylopectin (branched).
Cellulose: A linear polymer with extensive hydrogen bonding, making it water-insoluble.
Energy Storage vs. Structural Role:
Starch and glycogen serve as energy reserves, while cellulose provides structural integrity to plants.
7. Digestion of Carbohydrates
Enzymatic Breakdown: Starch and glycogen are hydrolyzed by enzymes like amylase into simpler sugars (maltose, glucose).
Lactose Intolerance: Occurs due to the inability to produce lactase, leading to difficulties digesting the disaccharide lactose due to a specific glycosidic bond.
8. Blood Types and Oligosaccharides
Oligosaccharides: Short chains of sugars that can serve as antigens in blood.
Examples: Type A and B blood types differ due to the presence or absence of specific sugar modifications on the blood cell surfaces (N-acetylgalactosamine for A, galactose for B).