Carbs!! Flashcards
Definition, composition, biological roles
organic molecules composed of carbon, hydrogen, and oxygen atoms in a ratio of 1:2:1
Carbohydrates also serve as structural components of cell walls
play a role in cell signaling and recognition
3 main classes of carbohydrates based on the number of saccharide units.
Monosaccharides
oligosaccharides
polysaccharides
What are aldoses and ketoses?
ald: contain an aldehyde functional group (-CHO)
ket: ketone functional group (C=O) in the molecule.
What are trioses, tetroses, pentoses and hexoses?
based on number of carbon atoms
(hexoses - most common and have D-glucose-aldohexose and D-fructose-hetohexose)
D- and L-stereoisomers of monosaccharides. Which of the two types are the predominant in living
organisms?
most hexoses are “D”
D (right) of reference carbon / chiral center
L (left) of reference carbon / chiral center
What are diastereomers? Examples?
NOTTT mirror images of each other (D-erythrosine and D-threose)
glyceraldehyde
dihydroxiacetone
ribose
glucose
mannose
galactose
fructose
- aldotriose
- only ketoriose
- 5-C aldopentose
- 6-C aldohexose
- EPIMER of glucose (c-2 atom)
-EPIMER of glucose (c-4)
-ketose form of glucose
Cyclization of monosaccharides: What is anomeric carbon? What are the α- and β-configurations of
the anomeric carbon
position of hydroxyl group determines if another is alpha or beta
In the α configuration, the hydroxyl group attached to the anomeric carbon is oriented downward (i.e., in the axial position) relative to the ring.
In the β configuration, the hydroxyl group attached to the anomeric carbon is oriented upward (i.e., in the equatorial position) relative to the ring.
Interconversion of α- and β-anomers in aqueous solutions
of D-glucose interconvert in aqueous solution by process called mutarotation
alpha is 33%
beta is 65%
What are furanose and pyranose forms of monosaccharides? Don’t miss it with pentoses and hexoses!
fur - 5 membered OXYGEN rings
pyr - 6 membered OXYGEN rings
What are reducing sugars? Which chemical group(s) in monosaccharide make them reducing?
they can donate electrons to another molecule during a chemical reaction
-monosaccharides reducing is the carbonyl group, which is either an aldehyde or a ketone
You are expected to know the structural formulas of the most common disaccharides and the types of
linkages they have between individual monosaccharides: maltose, lactose, and sucrose.
sucrose - table sugar
lactose - milk sugar
maltose - malt sugar
What feature determines whether a disaccharide is reducing or not?
non reducing when 2 sugar molecules can also be joined via glycosidic bond between 2 anomeric carbons
maltose and lactose is a reducing disaccharide
sucrose is a non-reducing disaccharide
Why lactose is a reducing sugar, while sucrose is not?
Since the anomeric carbon of glucose is involved in the glycosidic bond, it cannot form a hemiacetal or hemiketal, and it remains in the linear form. This means that the anomeric carbon of glucose in lactose is free to undergo oxidation and reduction reactions, making lactose a reducing sugar
Starch
main storage polysac in plants
amylose - long unbranched alpha 1,4
intertwined with
amylopectin - branched polymer points at 1,6
