Chem3Bsugars

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victimsofadown
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83588
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Chem3Bsugars
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2011-05-04 09:34:28
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Chem3Bsugars
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Chem3Bsugars
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  1. 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)
  2. What is the empirical formula of a monosaccharide?
    The most reduced formula for a monosaccharide is CH2O
  3. Aldose vs ketose. How to name?
    • Aldose - polyalcohol of aldehydes
    • 2-ketose - polyalcohol of ketones
    • All sugars end in -ose
  4. 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
  5. 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
  6. D-Glyceraldehyde
  7. Dihydroxyacetone
  8. D-Ribose
    • Important in RNA, DNA, and ATP
  9. D-Glucose
    • Grape sugar, blood sugar, dextrose
    • Most common hexose aldose sugar
  10. D-Fructose
    • fruit sugar
    • twice as sweet as sucrose
    • converted to glucose in blood stream
  11. What is an epimer?
    2 sugars that differ only at a single (non D/L) asymmetrical carbon
  12. fischer projection vs haworth projection
    • Fischer - "straight line" sugars in solid form
    • Hawoth - "circular" sugars in aqeous solution
  13. 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
  14. 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
  15. 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]
  16. How is maltose derived?
    Formed when starch (grain, a polymer of glucose) is broken down
  17. 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)
  18. 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
  19. Converting non-anomeric OH groups to hawarth projection.
    • OH on left -> OH up
    • OH on right -> OH down
  20. 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
  21. 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
  22. 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]
  23. What are the body's oxidizing/reducing agents?
    • NAD+ - oxidizing agent
    • NADH - reducing agent
    • FAD+ - oxidizing agent
    • FADH - reducing agent
  24. Molisch test
    • 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.
  25. Iodine test
    • Tests for presence of polysaccharides (not cellulose)
    • Blue, red, purple = positive test
  26. Benedict 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)
  27. Barfoed test
    • distunguishes between reducing monosaccharides and reducing disaccharides.
    • Similar to Benedict, but carried out in acidic medium
    • Reducing monosaccharides ONLY give a positive test
  28. Hydrolysis of Disaccharides
    • Disaccharides hydrolized in acidic medium to form their monosaccharide parts
    • Tested using Benedict's reagant afterward
  29. Bial test
    • Differentiates between pentoses and hexoses
    • Strongly acidic conditions
    • Blue color is a positive test for a pentose, all other colors are negative
  30. Seliwanoff Test
    • 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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