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Pre-Vet 3 > 7. Carbohydrates > Flashcards

7. Carbohydrates Flashcards

1
Q

What is the general formula for hydrates of carbon

A

Cm(H2O)n

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2
Q

What are saccarides and their functions (4)

A

They are sugars responsible for
1. Energy transport and storage
2. Structural (ex. bacterial cell walls, cellulose)
3. Information (ex. signals on proteins and membranes)

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3
Q

Oligosaccharides vs polysaccharides (2)

A

Oli: several sugar units
Poly: long chains of 100’s-1000s

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4
Q

When something ends in -ose, what does it refer to? (1)

A

of C’s in 1 unit

  1. used to name sugars
  2. prefix is how many carbons it has
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5
Q

How are aldoses and ketoses derived, and how are they classified based on carbon number (3-6)?

A
  1. The Aldoses derive from D-Glyceraldehyde
  2. Ketoses from Dihydroxyacetone
  3. The carbon numbering starts with the end of the molecule nearest the carbonyl carbon.
  4. Aldotrioses and ketotrioses have 3 C’s in the backbone.
  5. Aldotetroses and ketotetroses have 4 C’s.
  6. Pentoses and hexoses have 5 and 6 C’s.
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6
Q

What is the significance of D- and L-glyceraldehyde in assigning stereochemistry to sugars?

A
  1. Except for dihydroxyacetone, all the aldoses and ketoses have asymmetric = chiral carbons.
  2. In nature, most sugars are D- most AA are L-.
  3. D- and L-glyceraldehyde are reference molecules for assignment of stereochemistry (absolute configuration)
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7
Q

What are enantiomers, and what are the diagrams above called? (2)

A
  1. Enantiomers: nonsuperimposable mirror images
  2. The diagrams above are called “perspective formulae”.
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8
Q

Explain the fisher projection formulae. Why is it D? (2)

A
  1. It retain the stereochemical information but use lines for the bonds.
  2. Why D-? The chiral C furthest from the C=O has the same configuration as D-glyceraldehyde
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9
Q

How do enantiomers interact with plane-polarized light? (1)

A

These molecules are optically active: they rotate the plane of monochromatic plane-polarized light in opposite directions. dextrorotatory (+) or levorotatory (-).

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10
Q

Diastereomers vs epimers vs cyclic forms (3)

A

Diastereomers: Non-mirror image stereoisomers. (1&3, 1&4, 2&3, 2&4)
Epimers: Diastereomers that differ in configuration at 1C.
(1 & 3 @ C2 1 & 4 @ C3 2 & 3 @ C3 2 & 4 @ C2)
Cyclic Forms: In general, Aldehyde + Alcohol to Hemiacetal

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11
Q

Explain the structure of hemiacetals (3)

A
  1. Aldehyde + Alcohol = Hemiacetal
  2. oxygen atom in the hydroxyl group (−OH) of the alcohol is nucleophilic and attacks the electrophilic carbon in the carbonyl group (C=O) of the aldehyde.
  3. The oxygen in the original carbonyl group becomes an −OH group.
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12
Q

Explain the structure of hemiketals (3)

A
  1. Ketone + Alcohol = Hemiketal
  2. The oxygen atom in the hydroxyl group (−OH) of the alcohol is nucleophilic and attacks the electrophilic carbon in the carbonyl group (C=O) of the ketone.
  3. The oxygen in the original carbonyl group becomes an −OH group.
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13
Q

What happens to chiral centres in hemiketals/hemiketals and what types of reactions are formed? (3)

A
  1. New chiral centres have been created
  2. Intermolecular reactions for organic compounds with a carbonyl group (ketones and aldehydes)
  3. Intramolecular reactions for sugars (ketoses and aldoses)
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14
Q

What causes these different conformations? What are these diagrams called and what do they show? (3)

A
  1. Rotation about C-C bonds
  2. Haworth diagrams
  3. They show aspects of stereochemistry
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15
Q

What is more stable? 5-membered structures or 6-membered structure? What are they called (2)

A
  1. 6 membered structures (less straining, energetically favored)
  2. Pyranoses because they are similar to pyran structures see photo
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16
Q

What is the anomeric carbon in cyclic sugars, and what are isomers that differ only at this carbon called? (2)

A
  1. isomers that differ only at the hemiacetal or hemiketal c
  2. anomeric C
17
Q

For a 6-membered ring structure, which carbon is the new asymmetric carbon?

A

C1

18
Q

Alpha-anomer vs beta-anomer

A
  1. Alpha: OH on C1 is on the OPPOSITE side of the ring to 6
  2. Beta: OH on C1 is on the SAME side of the ring as the C6
19
Q

In the conversion from a Fischer diagram to a Haworth diagram, where does the hydroxyl group (OH) on an asymmetric carbon typically go?

A

OH on asymmetric C on the RIGHT = fisher
DOWN = haworth diagram

20
Q

When are Fischer diagrams (straight chains) correct for sugars, and when are ring structures more stable?

A

Fisher diagrams (straight chains) are correct for sugars with 3 or 4 c, otherwise, ring structures are more stable

21
Q

Explain this diagram

A
  1. In water, all three forms of glucose exist in equilibrium
22
Q

What is mutarotation?

A

Interconversion that can be measured by the rotation of plane-polarized light

23
Q

Explain light rotation for alpha-D-Glc, beta-D-Glc (4)

A
  1. PURE alpha = +112
  2. PURE beta = +19
  3. Equilibrium = +53
    - 36% (112) and 64% (19) = +53
24
Q

Explain this diagram (6)

A
  1. Pyranose rings are not entirely planar
  2. Each configuration (alpha, beta) can exist in 2 “puckered” conformations
  3. E = equatorial (the group is in the plane or parallel to the planar part of the ring)
  4. Less steric hindrance if bulky groups go into the e positions
  5. A = axial - perpendicular to the planar part of the ring
  6. First diagram is more stable than the second diagram
25
Q

Explain this photo of 2 chair conformations of C-D-Glc (1)

A

Only B-D-Glc can put all bulky substituents in the equatorial position so it is a very stable and abundant molecule

26
Q

Summarize this photo (4)

A
  1. Pentoses can also form acetals
  2. By moving the O beside the alpha carbon (first carbon) to form a carbon ring
  3. Alpha-d-ribose has the OH on the bottom of the alpha carbon
  4. Beta-d-ribose has the OH on the top of the alpha carbon
27
Q

Explain these structures (6)

A
  1. Cyclic ketoses
  2. These rings are puckered: rings that adopt non-planar 3D shapes to reduce strain.
  3. Five membered ring is called furan: 4 carbons and 1 oxygen
  4. O bonds to alpha carbon (c1) and breaks the bond between OH and C=O and bond H to O.
  5. alpha-d-fructofuranose = OH on bottom
  6. beta-d-fructodfuranose = OH on top

Pre-Vet 3 (11 decks)

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