Carbohydrate Theory Flashcards
Generally, what is a carbohydrate’s chemical structure?
- a polyhydroxy aldehyde (R-CH=O) or ketone (R-CR’=O)
What is the simplest aldehyde-based carb?
And what are aldehyde-based carbs called generally?
glyceraldehyde
- glycerol w/ one end OH replaced by =O
- known as aldoses
What is the simplest ketone-based carb?
And what are ketone-based carbs called generally?
dihydroxyacetone
- glycerol w/ middle OH replaced by =O
- known as ketoses
How are carbs generally named based on the number of carbons they contain?
triose - 3 C
**tetrose **- 4 C
pentose - 5 C
hexose - 6 C
etc.
How can L or D configurations be determined via a simple, 2D
backbone-style carb structure?
What configuration are most carbs in nature?
Look at the last chiral carbon in the chain.
The position of the functional group (OH) on this carbon determines L or D.
Most are D in nature.
How would a 6 C aldehyde-based carb be named?
An 8 C ketone-based carb?
Aldohexose
Keto-octose
etc.
How is D-Galactose different from D-Glucose?
What does this make it in relation to glucose?
How can its structure be rememberd?
- swapped OH position on C4 (left instead of right)
- this makes it the 4-epimer of glucose
- the OHs kind of make a G shape (according to Sipeki)
What is an epimer?
- an isomer that differs in configuration from its pair epimer at only one stereocenter
- ALL other stereocenters, if there are any, are the same
What is mannose in relation to glucose?
a 2-epimer
What does reduction of a carb consist of?
What is the product?
- aldehyde or ketone is reduced into primary or secondary alcohol, respectively
- in other words =O becomes -OH and -H
- makes a sugar alcohol
ex: glucose/fructose > sorbitol
What does a sugar oxidation consist of?
What does it make (3 examples via 3 diff oxidations) ?
- generally a group that has either only -OH or =O gets BOTH and becomes carboxylic
- 1st group = -aldonic acid
- last group = -uronic acid
- both groups = -aldaric acid
How is fructose different from glucose?
Using general nomenclature, what does this make it?
- the =O is on C2 via a spontaneous migration
- this makes it a ketohexose (rather than aldo-)
What are some examples of important sugar alcohols and their functions in nature?
**ribitol **is a component of riboflavin (vit B2)
**sorbitol **is used as a sweetener for diabetics
What are some important natural sugar acids and their functions?
**D-glucuronic acid **and uronic acid are mucopolysaccharide components
L-ascorbic acid is vitamin C
D-glyceric acid is important to glycolysis and O2 binding in Hb
Why don’t carbohydrates exist in the open chain form in which they are often represented?
- because aldehyde and ketone groups are quite reactive
- tend to form rings with other Os in the chain