Card Set Information
What defines an asymetrical carbon? How does this relate to the number of stereoisomers a monosaccharide can form?
A C with 4 different groups attached
# of stereoisomers = 2
(n= # of asymetrical C atoms)
What is the empirical formula of a monosaccharide?
The most reduced formula for a monosaccharide is CH
Aldose vs ketose. How to name?
Aldose - polyalcohol of aldehydes
2-ketose - polyalcohol of ketones
All sugars end in -ose
Describe D vs L sugars. What is "natural?"
D/L is determined by the OH group on the last asymmetrical C (farthest from carbonyl)
OH to the right = D
OH to the left = L
All natural sugars are D
What defines a triose, tetrose, pentose, and hexose? How many isomers will each have (aldose form)? In 2-ketose form?
Defined by total # of carbons (not asymm)
triose=2, tetrose=4, pentose=8, hexose=16
triose=0, tetrose=2, pentose=4, hexose=8
Important in RNA, DNA, and ATP
Grape sugar, blood sugar, dextrose
Most common hexose aldose sugar
twice as sweet as sucrose
converted to glucose in blood stream
What is an epimer?
2 sugars that differ only at a single (non D/L) asymmetrical carbon
fischer projection vs haworth projection
Fischer - "straight line" sugars in solid form
Hawoth - "circular" sugars in aqeous solution
How to recognize an enzyme? General enzymes related to monosaccharides and their functions?
name ends in -ase, describes function
Isomerase - converts various isomers (glucose-fructose isomerase)
Epimerase - converts various epimers
D-Galactose (no structure)
C4 epimer of D-Glucose
Galactosemia is when a person does not have the enzyme to convert galactose to glucose, those afflicted cannot have lactose
Name the disaccharides, their components, their function/location, and their linkage.
: galactose + glucose - milk sugar [β-1,4 glycosidic linkage]
: fructose + glucose - table sugar, beat sugar, cane sugar [α-1,2 glycosidic linkage]
: glucose + glucose - malt sugar, malt liquor, cereal, candy [α,β-1,4 glycosidic linkage]
How is maltose derived?
Formed when starch (grain, a polymer of glucose) is broken down
Name the polysaccharides, their function/location, their linkage, and general info about all polysaccharides
Condensation polymers which have glucose as their monomer; polyethers
Cellulose - plant stucture [β-1,4 (straight chain)]
Starch - plant energy storage [80% α-1,4; 20% α-1,6 (some branching)]
Glycogen - animal energy storage [α-1,4; much more α-1,6 (highly branched)]
Humans cannot break down the β linkage (cellulose is passed though the body)
What is an anomer?
2 sugars that differ only at the anomeric carbon (α or β)
α - OH on anomeric carbon is down
β - OH on anomeric carbon is up
β more common in the body
Converting non-anomeric OH groups to hawarth projection.
OH on left -> OH up
OH on right -> OH down
pyranose vs furanose
: 5 carbons in ring, O between C5 and C1, C6 extends from C5 - formed from aldose hexoses
: 4 carbons in ring, O between C2 and C5, C1 extends from C2, C6 extends from C5 - formed from aldose pentose and 2-ketose hexose sugars
What is a reducing sugar? Give examples.
A sugar that will reduce other substances (become oxidized) - can be tested using benedict's reagent
glucose, fructose, glyceraldehyde, galactose, lactose and maltose
Ketoses are converted to aldoses, then oxidized
sucrose is NOT a reducing sugar
Alditols vs aldonic acid vs adaric acid
Aldonic acid - formed from weak oxidizing agent, CHO converted to COOH on C1 [Br
Aldaric acid - formed from strong oxidizing agent, CHO converted to COOH on C1 and CH
OH converted to COOH on C5/6 [HNO
Alditol - formed from reducing agent, CHO converted to CH
OH on C1 [NaBH
What are the body's oxidizing/reducing agents?
- oxidizing agent
NADH - reducing agent
- oxidizing agent
FADH - reducing agent
General test for carbohydrates (differentiate mono, di, and poly)
Monosaccharides give a positive test quickly
Disaccharides/polysaccharides are slowly hydroyzed to produce monosaccharides and will give a slower positive test.
Tests for presence of polysaccharides (not cellulose)
Blue, red, purple = positive test
Tests for the presence of a reducing sugar
Will form brick-red, brown, green, or yellow precipitate
Carried out in basic medium
(Not sucrose, starch)
distunguishes between reducing monosaccharides and reducing disaccharides.
Similar to Benedict, but carried out in acidic medium
Reducing monosaccharides ONLY give a positive test
Hydrolysis of Disaccharides
Disaccharides hydrolized in acidic medium to form their monosaccharide parts
Tested using Benedict's reagant afterward
Differentiates between pentoses and hexoses
Strongly acidic conditions
Blue color is a positive test for a pentose, all other colors are negative
Distinguishes between ketohexoses and aldohexoses
React to form a red-colored product
Amount of time it takes for red color to appear determines test result
Ketohexoses appear red quickly (~2 min)
Disaccharides and polysaccharides will EVENTUALLY hydrolize to hexoses