Chem Chapter 5

  1. Chapter 5: Carbohydrates: Life’s Sweet Molecules
  2. Carbohydrate
    Carbohydrate – sugar composed of C, H, and O. A primary source of energy in a normal diet.

    Most carbohydrate names end in –ose.Glucose, fructose, lactose, etc
  3. Carbohydrates
    Simple carbs are called “simple sugars” and often taste sweet.

    Simple sugars break down quickly; if we consume too many, they are converted to fat.

    Complex sugars take longer to break down.
  4. Carbohydrates
    • Not just used for energy
    • –Found on surfaces of cells and allow molecules to distinguish one cell from another

    –ABO blood markers are carbs found on red blood cells which allow us to distinguish our body’s blood type from another.
  5. Carbohydrates
    Heparin – a carb used by the body to prevent blood clots

    Carbs also found in DNA and RNA
  6. Monosaccharides
    Monosaccharides – simplest carbs, often sweet-tasting. Cannot be broken down into smaller carbs.
  7. Glucose
    Glucose – C6H12O6
  8. Disaccharides
    Disaccharides – two monosaccharide units joined together. Can be split into two monosaccharide units.
  9. Sucrose
    Sucrose – C12H22O11 – can be split (hydrolyzed) into two monosaccharides: glucose and fructose
  10. Oligosaccharides
    Oligosaccharides – carbs containing anywhere from 3 to 9 monosaccharide units

    –ABO blood-typing groups are oligosaccharides.
  11. Polysaccharides
    Polysaccharides – 10 or more monosaccharide units joined together

    –Sugar units can be connected in one continuous chain or the chain can be branched.
  12. Section 5.2: Monosaccharides
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    • General formula: Cn(H2O)n, n ≧ 3

    • Two kinds of functional groups
    • –Hydroxyl (f.c. = alcohol): -OH
    • –Carbonyl (f.c. = aldehyde or ketone): C=O
  13. Alcohols
    • Classified by # of alkyl groups attached to alcoholic carbon
    • –Primary (1o) alcohol: 1 alkyl group
    • –Secondary (2o): 2 alkyl groups
    • –Tertiary (3o): 3 alkyl groups

    Monosaccharides contain 1o and 2o alcohols.
  14. Alcohols
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  15. Aldehydes
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    Carbonyl group with a hydrogen bonded to one or both sides of the carbon

    • Formaldehyde
    • –Once used as a biological preservative
    • –H on both sides
  16. Ketones
    Carbonyl group with an alkyl or aromatic group on both sides of the carbonyl carbon

    • Acetone
    • –Once the main ingredient in fingernail polish remover
    • –Methyl group on both sides
  17. Aldehydes vs. Ketones
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    • The top is Ketone & the bottom is Aldehyde.
  18. Monosaccharides
    • M.S. w/ aldehyde = aldose
    • M.S. w/ ketone = ketose

    • M.S. w/ three C = triose
    • Four = tetrose
    • Five = pentose
    • Six = hexose
  19. Glucose
    • Glucose
    • –Aldose w/ six carbons
    • –Aldohexose
  20. Fructose
    • Fructose
    • –Ketose w/ six carbons
    • –Ketohexose
  21. Stereochemistry in Monosaccharides
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    •How many chiral carbons does glucose have?
  22. Stereochemistry
    4 chiral carbons means 16 (24) possible stereoisomers for glucose!

    We need an easier way to draw monosaccharides.
  23. Fischer Projections
    Horizontal lines on a chiral center represent wedges.

    Vertical lines on a chiral center represent dashes.

    C atoms are understood at the intersections.
  24. Fischer Projections
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  25. D-sugars & L-sugars
    D-sugars have the –OH on the chiral carbon farthest from the carbonyl on the right side.

    • Most carbs in nature are D-sugars.
    • –The carbs we use for energy are D-sugars.

    L-sugars have the –OH on the chiral carbon farthest from the carbonyl on the left side.

    (Tip: L-sugar = Left side)
  26. Fischer Projections
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    Remember: Enantiomers are mirror images: all chiral carbons are opposite.
  27. Diastereomers
    There can only be 1 mirror image for any stereoisomer.

    –What about the other 14 stereoisomers?

    Diastereomers – stereoisomers that are not enantiomers

    –Different names: galactose and talose are diastereomers of glucose
  28. Important Monosaccharides
    Several of the most common monosaccharides are hexoses.

    –Produced and used only as D-isomers.
  29. Glucose
    • –D-glucose is commonly called dextrose, blood sugar, and grape sugar
    • –Found in fruits, vegetables, and corn syrup

    –Broken down by the body during glycolysis to provide energy

    –Monitored by diabetics
  30. Diabetics

    –Glucose doesn’t undergo glycolysis as easily

    –Glucose may build up

    –Blood becomes corrosive, damaging body systems
  31. Galactose
    –Galactose + glucose = lactose (milk sugar)

    –1 chiral center on C4, arranged opposite C4 on glucose

    –Can be converted to glucose by the body

    –Diastereomers that differ in just one chiral center are called epimers.
  32. Galatosemia
    –Rare genetic disorder

    –Body breaks lactose into glucose and galactose

    –Body lacks enzymes needed to further metabolize galactose

    –Toxic build-up of galactose-1-phosphate

    –NOT the same as lactose intolerance
  33. Mannose
    –Another epimer of glucose

    –Not easily absorbed by the body

    –Used to treat UTI

    –Bacteria in the bladder attach to mannose and can be eliminated
  34. Fructose
    –“Fruit sugar” or “levulose”

    –Found in fruits, vegetables, and honey

    –70% sweeter than glucose

    –Same sweet taste, fewer calories!
  35. DNA and RNA
    DNA and RNA differ in their name based on the monosaccharide they contain.

    Deoxyribonucleic acid (DNA) – 2-deoxyribose

    Ribonucleic acid (RNA) – ribose

    Only difference: Absence of an oxygen on C2 of deoxyribose
  36. Section 5.3: Oxidation and Reduction Reactions
  37. Oxidation
    Oxidation – loss of e- from one species in a chemical rxn
  38. Reduction
    Reduction – gain of e- by one species in a rxn
  39. Redox Reactions
    Oxidation and reduction always occur together in redox reactions.
  40. Reducing Agent
    The species that is oxidized is called the reducing agent.

    –It causes reduction of the other species.
  41. Oxidizing Agent.
    The species that is reduced is called the oxidizing agent.

    –It causes oxidation of the other species.
  42. Redox Reactions
    • OIL-RIG
    • –Oxidation Is Loss (of e-)
    • –Reduction Is Gain (of e-)

    • In organic molecules…
    • –Oxidation: gain of O or loss of H
    • –Reduction: loss of O or gain of H
  43. Monosaccharides and Redox
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    • In aldoses…
    • –Oxidation and reduction occur at the C=O.
    • –Can oxidize to a carboxylic acid or reduce to an alcohol
  44. Benedict’s Test
    Oxidized molecules reduce other substances.

    Benedict’s Test – addition of Cu2+ ions (blue) to a sugar

    –Aldehyde is oxidized to a sugar acid by Cu2+.

    –Cu2+ is reduced to Cu+ by the aldehyde.

    –Cu+ forms Cu2O (brick red), indicating the presence of a “reducing sugar” (aldose)
  45. Benedict’s Test
    Reducing sugar – a sugar capable of reducing another substance, like Cu2+

    Benedict’s test can be used to monitor glucose levels in urine.

    –Excess glucose in urine suggests high levels of glucose in the bloodstream, an indicator for diabetes.
  46. Sugar Alcohols
    Reduction of aldoses or ketoses produces sugar alcohols.

    –Used as artificial sweeteners in sugar-free foods.

    Produced from excess glucose in the blood.

    –Glucose reduces to sobitol, which, at high concentrations, can contribute to cataracts.

    –“Sugar cataracts” commonly seen in diabetics.
  47. Section 5.4: Ring Formation – The Truth About Monosaccharide Structure
  48. The Truth About Monosaccharide Structure
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    Carbonyl groups can react with hydroxyl groups.

    When this happens, the product contains the hemiacetal functional group.
  49. Hemiacetal
    Hemiacetal – an –OH group and an –OR group attached to the same carbon

    M.S. contain both a carbonyl and several hydroxyl groups.

    –F.G. can react within the same molecule.
  50. Monosaccharide Structure
    -OH on the 2nd carbon from the end curls around to react with the carbonyl carbon.

    • –A ring containing an O is formed, with one carbon left outside the ring.
    • M.S. exist in a ring form most of the time
  51. Cyclic structure
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  52. Anomers
    Carbonyl carbon shape: trigonal planar

    –-OH group can attach on either the top or the bottom.

    –Produces two different stereoisomers, called anomers.

    –In a ring, the carbon from the carbonyl carbon is called the anomeric carbon

    – it is the only carbon directly bonded to two oxygen atoms.
  53. Anomers
    Anomers are either alpha (α) or beta (β).

    –α: if –OH on anomeric C is on the opposite side of the ring from the C that is outside the ring

    –β: if –OH on anomeric C is on the same side of the ring as the C that is outside the ring
  54. Pyranose
    • Pyranose – any cyclic sugar containing a ring made of 5 C atoms and an O atom
    • –Typically formed from an aldose
  55. Furanose
    • Furanose – any cyclic sugar containing a ring made of 4 C atoms and an O atom
    • –Typically formed from a ketose
  56. Anomers
    For 6-C sugars, C-6 is always drawn on the top side of the ring.
  57. Anomers
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  58. Alpha or Beta?
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  59. Alpha or Beta?
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  60. Alpha or Beta?
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  61. Section 5.6: Polysaccharides
  62. Storage polysaccharides
    Storage polysaccharides – P.S. that are stored in cells as a glucose energy reserve

    –α-glucose M.S. are connected into polysaccharides.
  63. Storage Polysaccharides - Plants
    • Starch is a mixture of two P.S.
    • –Amylose
    • –Amylopectin

    As fruit ripens, the enzyme amylase hydrolyzes (breaks, using water) glycosidic bonds in starch, producing glucose and maltose, which taste sweet.
  64. Storage Polysaccharides - Animals
    Animals store glucose as the P.S., glycogen.

    –Mostly found in liver and muscles

    Hydrolyzed to glucose in the liver, sent into the bloodstream

    Used to maintain glucose levels during fasting periods
  65. Structural Polysaccharides
    Structural polysaccharides – P.S. whose function is to provide structure for an organism

    β-glucose M.S. are connected into polysaccharides.
  66. Structural Polysaccharides
    Cellulose – P.S. that provides plant structure

    –Called “insoluble fiber” because we lack the enzyme, cellulase, required to digest it.

    Obtained in our diet via whole-grain foods

    –A component of “dietary fiber”

    Assists with digestive movement in small and large intestines
  67. Structural Polysaccharides
    Chitin – P.S. that makes up exoskeletons of insects and crustaceans and cell walls of some fungi

    Present in surgical thread that biodegrades as a wound heals

    Used in cosmetics and lotions to hold in moisture
  68. Section 5.7: Carbohydrates and Blood
  69. Carbohydrates and Blood
    Blood types – A, B, AB, O – refer to carbohydrates.

    Carbs act as chemical markers on red blood cells.

    –They identify your cells as yours, and not as those of a pathogen.
  70. ABO Blood Markers
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    Contain either three or four of the following M.S. units:
  71. ABO Blood Markers
    • All blood types include
    • –N-acetylglucosamine
    • –Galactose
    • –Fucose

    Type O blood contains only these three carbs attached to the RBC surface via a glycosidic bond.
  72. ABO Blood Markers
    Types A and B contain these three carbs, plus one extra, bonded to the galactose unit.

    • –Type A contains N-acetylglucosamine.
    • –Type B contains a second galactose.

    Type AB has both Type A and Type B carb sets on the RBC.
  73. ABO Blood Markers
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  74. ABO Blood Markers
    • O
    • –universal donor
    • –Carb set for O is present in ALL blood markers
    • –Body never sees Type O as an invader

    • AB
    • –universal acceptor
    • –AB carb set contains all other types of blood marker
    • –Body sees all types of blood as its own
  75. Heparin
    Heparin – P.S. that prevents blood clotting (anticoagulant)

    –Test tubes, tubing, and needles used for drawing blood are normally coated with heparin.

    Belongs to a group of P.S. called glycosaminoglycans, which have highly charged repeating disaccharide units
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Chem Chapter 5
Chapter 5 Fimnal Review