Chapter 4 - Carbohydrates Flashcards
What is the structure of Dihydroxyacetone?
What is the structure of glyceraldehyde?
What do you call carbohydrates that have aldehydes as their most oxidized functional group?
aldoses
What do you call carbohydrates that have ketones as their most oxidized functional group?
ketoses
What are the common names for the 4 most important monosaccharides?
D-fructose, D-glucose, D-galactose, D-mannose
What is the structure of D-fructose?
What is the structure of D-glucose?
What is the structure of D-galactose?
What is the structure of D-mannose?
What is the formula for figuring out the number of stereoisomers for a multi-chiral carbon compound?
2n
Where n is the number of chiral carbons present.
What system should we use in denoting the absolute configuration of the biomolecule carbohydrates?
D and L.
While organic chemists use the newer R and S system, Biochemists use the older D and L system.
Note R and S is not interchangeable with D and L.
How are the optical rotation of monosaccharides determined?
experimentally.
( + ) and ( - ) are not related to D and L absolute configuration of the sugar.
What are the 3 different types of stereoisomers for sugars?
- Enantiomers
- Diastereomers
- Epimers
What are diastereomers?
Stereoisomers that are chiral, share the same connectivity but are not mirror images of each other. They have more than 1 chiral carbon.
What are enantiomers?
Two molecules that are non-superimposable images of one another.
What are epimers?
They are a special subtype of diastereomers that differ in configuration at exactly one chiral center.
What is the anomeric carbon?
The anomeric carbon is a carbonyl carbon that becomes a new stereo centre during cyclization.
it is special type of epimer.
How do you convert Fischer Projection sugars to Haworth Projections?
The -OH groups on the right side of the Fischer Projections will be pointing down in Haworth projections.
What’s more stable, the alpha-anomer or the beta anomer of D-glucose?
The beta anomer is more stable. the alpha anomer has the anomeric -OH in axial position which increases steric hindrance.
What are Tollen’s Reagent (Ag(NH3)2) and Benedict’s reagent (Cu(OH)2) used for?
To test for the presence of reducing sugars (sugars that could undergo further oxidation).
What does Tollen’s reagent (Ag(NH3)2) do?
It is an oxidizing agent that oxidize aldoses, to test for their presence.
What does Benedict’s reagent (Cu(OH)2 ) do?
It is an oxidizing agent that oxidize aldoses, to test for their presence.
