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25 Cards in this Set
- Front
- Back
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What is an aldose?
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a sugar with an aldehyde group at one end
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What is a ketose?
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a sugar with a ketone at the C2 position
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What are the functions of carbohydrates?
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1. energy storage
2. cell-cell recognition 3. cell wall formation 4. coenzymes 5. nucleic acid composition 6. glycoconjugates, i.e. glycoproteins |
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Chirality of sugars
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L- first chiral center -OH is to left
D- first chiral center -OH is to right Note: almost all sugars in the body are D |
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How do sugars cyclize?
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nucleophilic attack by the an alcohol to the carbonyl of C1 leads to formation of a 5 or 6 membered ring
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What is an anomer and how are they classified?
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An anomer is the most oxidized carbon on a cyclized sugar molecule. If the -OH is above the ring it is a beta anomer. If the -OH is below the ring it is an alpha anomer.
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How do you name a cyclized sugar?
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type of anomer - root name of sugar + type of ring
furanose - 5 membered ring pyranose - 6 membered ring ex. alpha-galactopyranose |
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What are the conformations of a furanose?
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1. If C2 projects out of the plane - C2-endo envelope
2. If C3 projects out of the plane - C3- endo envelope 3. If C3 projects up and C2 projects down - twist conformation |
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What are the conformations of a pyranose?
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1. Chair conformation - most energetically favorable
2. Boat conformation |
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What is a glycosidic bond?
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an ester bond between two monosaccharides using the alcohol of the anomeric carbon
-or- formation of an acetal between the -OH of the anomeric carbon and a carbon on another sugar |
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Maltose
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alpha-D-glucopyranosyl
alpha C1 to C4 bond beta-D-glucopyranose |
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Cellubiose
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beta-D-glucopyranosyl
beta C1 to C4 bond beta-D-glucopyranose |
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Lactose
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beta-D-galactopyranosyl
beta C1 to C4 bond alpha-D-glucopyranose |
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Sucrose
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alpha-D-glucopyranosyl
alpha C1 to beta C2 bond beta-D-fructofuranoside |
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Amylose
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Starch
Sugars: glucose Linkages: alpha C1 to C4 |
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Amylopectin
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Starch
Sugars: glucose Linkages: alpha C1 to C4 branches at alpha C1 to C6 |
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Glycogen
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Sugars: glucose
Linkages: alpha C1 to C4 branches at alpha C1 to C6 |
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Cellulose
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Sugars: glucose
Linkages: beta C1 to C4 Note: this is not digestible by mammals. ruminant animals have digestive bacteria that break this down for them. |
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alpha amylase
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present in saliva
breaks alpha glycosidic bonds endoglycosidase- works on the center portions of starches products are glucose and maltose |
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beta amylase
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present in saliva
breaks alpha 1-4 glycosidic bonds exoglycosidase- works from the end of the chain by breaking the non-reducing end of the bond product is maltose |
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what is a reducing sugar?
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A sugar capable of participating in oxidation-reduction reactions as an reducer (electron donor)
this is the anomeric carbon on aldoses Note: Sucrose is NOT a reducing sugar. |
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What are the tests for a reducing sugar?
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1. Tollen's test: addition of Tollen's reagent (silver salt) leads to the formation of a silver mirror
2. Benedict's Test- addition of Benedict's reagent (copper salt) leads to a red copper precipitate |
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Maltase
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substrates: maltose and maltotriose
products: glucose |
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Sucrase
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substrates: sucrose
products: glucose and fructose |
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Lactase
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substrates: Lactose
products: glucose and galactose Note: All humans express this early in life, but most stop expressing this protein as they age. Some Northern Europeans have evolved to express this protein throughout life. |
