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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 = 2n (n= # of asymetrical C atoms)
What is the empirical formula of a monosaccharide?
The most reduced formula for a monosaccharide is CH2O
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
- fruit 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
- brain sugar
- 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.
- Lactose: galactose + glucose - milk sugar [β-1,4 glycosidic linkage]
- sucrose: fructose + glucose - table sugar, beat sugar, cane sugar [α-1,2 glycosidic linkage]
- maltose: 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
- Pyranose: 5 carbons in ring, O between C5 and C1, C6 extends from C5 - formed from aldose hexoses
- Furanose: 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 [Br2/H2O]
- Aldaric acid - formed from strong oxidizing agent, CHO converted to COOH on C1 and CH2OH converted to COOH on C5/6 [HNO3]
- Alditol - formed from reducing agent, CHO converted to CH2OH on C1 [NaBH4 or LiAlH4]
What are the body's oxidizing/reducing agents?
- NAD+ - oxidizing agent
- NADH - reducing agent
- FAD+ - 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
- Acidic environment
- 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
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