carbs Flashcards
How are carbohydrates synthesized? what types of moleucles are they?
Via photosynthesis
- aldoeses and ketoses
CO2 + H2O + light energy → Sugar + O2
What are the three types of carbohydrates?
- Monosaccharides
- Oligosaccharides
- Polysaccharides
what is the major source of digetsible carbs in the human diet? what is the least?
carbs provide ~80% of the calories in humans diets
Most: starch
Least: glucose
What functional groups do monosaccharides contain?
- Hydroxyl (-OH) groups
- Aldehyde (-CHO) or ketone (-CO) groups
What characterizes aldoses and ketoses?
- Aldoses: Contain an aldehyde group (e.g., glucose)
- Ketoses: Contain a ketone group (e.g., fructose)
What structure is naturally occuring glucose found in?
D-glucose
What is the D- and L-system based on?
The position of the OH group on the highest numbered chiral carbon
In the D- and L-system, where is the -OH group located for D-sugars? what about L?
On the right
On the left
What is the formula to determine the number of stereoisomers? how many possible sterioisomers exist for glucose?
2ⁿ, where n is the number of chiral centers
-16 for glucose (4 chiral centers)
What is D-Fructose commonly known as? where is it found?
Fruit Sugar or Levulose
-found in fruits, honey, HFCS (sweeter than glucose)
What type of sugar is this? how many chiral C does it have? how many sterioisomer possibilities?
D-fructose (ketose sugar)
-3 chiral C (8 isomers)
What is the rosanoff projection?
projection that indicates OH groups by horizontal bonds
-aldehydes depicted with O
- ketones depicted with C=O
what is the importance of base/enzyme catalyzed isomerization? what enzyme is used?
it allows us to form D-fructose from D-Glucose (sweeter product)
-glucose isomerase
how do ketoses and aldoses relate in terms of nomenclature? (D-arabinose vs D-Fructose)
Aldose sugars with the same structure are named to reflect that
-D-arabinose (aldose) is also called D-arabinohexulose for the ketone form
What are the two main cyclic forms of monosaccharides? what distinguishes these two forms?
- Pyranose (6-membered ring)
- Furanose (5-membered ring)
What is the reaction to form a hemiacetal? why is this important?
Aldehyde + Alcohol
-hemiacetal formation is needed to produce ringed sugar as the rxn can occur within the same aldose / ketose
What is an α-anomer?
-OH group below the plane of the ring
(opposite side of the CH2OH group on C5)
What is a β-anomer?
-OH group above the plane of the ring (same side as the CH2OH group on C5)
What is mutarotation?
The interconversion of α- and β-anomers via the open-chain form.
What conformation do pyranose rings adopt for stability?
Chair conformation
What is the more stable position in the chair conformation? what impact do anomeric OH have on stability?
Equatorial position
-OH on the anomeric carbon can increase the stability of alpha conformations
explain the notation of the chair conformation
the number above indicates that C4 is above and C1 is below
What tautomeric forms does fructose exist in? what is the dominant form?
- β-pyranose
- β-furanose
- pyranose is favoured
What tautomeric forms does glucose exist in? what is the dominant form?
In aq solution, formation of furanose rings are very rare
-pyranose rings are predominant form from D-glucose
