Carbohydrates Flashcards
Saccharides
Simplest sugar
Monosaccharides
Simplest, 1 unit of sugar
Alcohol
- Polar
- Hydrogen bonding
- Water soluble
- Nucleophile
Ether
- Not reactive on its own
- Reactive when next to OH
Axial
Axial = Alpha
Axial = 6 membered ring takes the chair position
When are substituents on 6-membered rings more stable?
Substituents on 6-membered rings are usually more stable when equatorial
What is the anomeric effect?
The conformation is inverted when an electronegative group is next to an oxygen in the ring.
When you have an oxygen in a ring with an oxygen next to it, what position would it rather be?
Axial position
Anomeric configuration
Alpha or Beta
Absolute sterochemistry
D or L
Usually D in nature
Aldehydes are…
Aldehyde are easy to oxidise = reducing sugars
Glycosides
Non-sugar
Small non-sugar molecules attached through an anomeric position to a sugar
Aglycon
Own
Small molecule part on its own
What form are many natural products found in?
- Glycosides
- This is the form in which many natural products usually exist, since it allows organisms to store compounds in an inactive form
When does glycosylation happen?
During metabolism of compounds in the body
What are glycans?
Cell surface
Glycans are complex saccharides found on the cell surface
What is the key role of glycans?
Cells
Recognition of cells
Energy/metabolism
Oxidation, combustion
- Sugars are a source of energy based upon the favourable oxidation of carbon
- It provides an accessible source for the controllable equivalent of combustion
Formula for sugars/carbohydrates
[CH2O]
When do monosaccharides exist in equilibrium?
Acetal
Monosaccharides exist in equilibrium between different 5- and 6-membered rings because of acetal chemistry
The anomeric effect…
The anomeric effect gives preference to axial hydroxyl
What are the main functions of carbohydrates?
- Energy source
- Structure
- Recognition
