Gastrointestinal tract

Carbohydrates

By medgroww

Posted on April 3, 2023

Classification

Estimated reading time: 3 minutes

Aldehydes and ketones derivatives of polyhydric alcohols

Classification

Monosaccharides

Sugars that cannot be hydrolyzed into simpler carbohydrates
Types

	Aldoses	Ketoses
Trioses	Glycerose (Glyceraldehyde)	Dihydroxyacetone
Tetroses	Erythrose	Erythrulose
Pentoses	Ribose	Ribulose
Hexoses	Glucose, Galactose, Mannose	Fructose

Disaccharides

Isomers

Compounds with same molecular formula but different structure
Types

Optical isomers

Compounds with same molecular, chemical & physical properties but different in their effect on rotation of polarized light
↓
Asymmetric carbon atoms on compound
↓
Plane-polarized light beam is passed through a solution of an optical isomer
↓
Plane-polarized light beam rotates either to right or left
↓
Right (Clockwise) : Dextrorotatory (+): d (+)
Left (Anti-clockwise) : Levorotatory (–): l (-)
↓
In solution, glucose is dextrorotatory → Glucose solutions : Dextrose

Racemic mixture = 1 : 1 of d & l → No optical activity

Stereoisomers

Compounds with same molecular formula & constitution but different spatial orientation
Types
- Enantiomers
  - Non-superimposable mirror image
  - Different spatial orientation of -OH groups on penultimate carbon atom
  - Types
    - D-isomer : -OH group on right
    - L-isomer : -OH group on left
  - Most of naturally occurring monosaccharides are D sugars, and enzymes responsible for their metabolism are specific for this configuration
  - Racemase enzyme interconverts D & L isomers
- Diastereomers
  - Not mirror image
  - Types
    - Epimers
      - Different configuration of -OH group on carbon atoms 2 or 3 or 4
      - Epimers of glucose
        
        C2 epimer : Mannose
        
        C3 epimer : Allose
        
        C4 epimer : Galactose
    - Anomers
      - Reaction between aldehyde or ketose & alcohol group
      - Reaction between C1 (aldehyde) & C5 (alcohol) of glucose
        
        Ring structure: Pyranose ring >> Furanose ring
        
        Crystalline glucose : α-d-Glucopyranose >> α-d-Glucofuranose
        
        Glucose in solution : Cyclic structure retained, but isomerism occurs about position 1
        
        Anomeric carbon atom : C1
        
        Glucopyranose
        
        α-Glucopyranose (38%) : -OH group on C1 is below plane
        
        β-Glucopyranose (62%) : -OH group on C1 is above plane