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Biochem Exam 2 > 14 - Carbohydrates > Flashcards

14 - Carbohydrates Flashcards

1
Q

Isomer =

A

2 molecules same MOLECULAR formula

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2
Q

What is constitutional isomer?

A

change order of atoms (connectivity of atoms)

    • macromolecular constitutional isomers = TAUTOMERS
    • carbohydrate tautomers = aldose + ketose
    • relocation H+ –> bond order rearrangement (movement pi bond/carbonyl) NO break/form bonds!
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3
Q

Aldose + Ketose

A

Tautomers

– relocation H+ changes which C forms pi bond w/ O

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4
Q

where C # begin in carbohydrate structure?

A

starts terminal carbonyl C of aldose

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5
Q

What are stereoisomers?

A

change spatial orientation of atoms; fixed bond order (connectivity)

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6
Q

2 main stereoisomers + major differences:

A

Configurational isomers – chiral C’s and changes spatial orientation around chiral C
Conformational isomers – reversible rotation around single bond (nucleotide glycosidic bond)

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7
Q

How many chiral C are possible in 3 C sugar structure?

A

1

– Both terminal C always Achiral

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8
Q

Enantiomers

A

Mirror images @ ALL chiral centers

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9
Q

Distereomers

A
    • contain multiple chiral centers
    • NOT mirror images at ALL chiral centers

4-C sugar:

    • 2 chiral centers
    • 4 distereomers (2 pairs of enantiomers)
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10
Q

Fisher projection

A

– linear model of carbohydrate structure

structure

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11
Q

Haworth Projection

A

– cyclical 2D representation carb structure

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12
Q

Pyran ring

A
    • 6 member ring

- most 6-C carbs

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13
Q

Furan

A
  • 5 member ring

- - most 5-C carbs, except fructose (6-C)

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14
Q

What is anomeric C?

A

– Carbonyl C in linear structure and is the 1st C to right O in cyclic structure carbs

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15
Q

After cyclicization (carbonyl –> hydroxyl), how do you determine orientation (alpha vs beta) of hydroxy at anomeric C?

A

CANNOT determine alpha/beta orientation of OH from Fisher projection

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16
Q

alpha vs beta carbohydrate:

A

alpha carbohydrate – OH oriented DOWN

beta carbohydrate – OH = UP

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17
Q

2 types of Distereomers:

A

Anomers – differ ONLY orientation of OH @ anomeric C (1 alpha, 1 beta)

Epimers – SAME anomeric orientation but differ in OH orientation at any other C in ring (both alpha or both beta)

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18
Q

Configurational isomers

A

differ order (spatial orientation) around chiral C

19
Q

conformational isomers

A

REVERSIBLE free rotation around single bond

– think syn/anti nucleotides, endo/exo, sugar-pucker, boat/chair conformations

20
Q

FURANose vs PYRANose conformational isomers

A 
Furanose = 5-member rings; endo/exo conformations
Pyranose = 6-member rings; boat/chair conformations
21
Q

C3H6O3 =

A

Trioses common structure

22
Q

C5H10O5 =

A

Pentose common structure

23
Q

C6H12O6 =

A

Hexoses common structure

24
Q

Fucose =

A
    • Galactose derivative
    • only L-monosaccharide synth/used mammals
    • part A/B/O blood antigens
    • excess free blood fucose = liver damage, cancers, diabetes, heart disease

***L-enantiomer galactose + OH replaced CH3 (mod forms C-C bond, rare)

25
Q

Phosphorylation modifications

A
    • Ester linkages
    • part nucleic acids
  • -**important reactive intermediates of carb metabolism
      • negative charge to sugar
    • name molecule tell you where phosphate located in molecule
26
Q

Oxidation modifications

A

REDUCING SUGARS

    • oxidized @ carbonyl-C (anomeric)
    • 2 step process creating acid + lactones
    • old diabetes urine tests looked reducing sugars as indicator high blood glucose concentrations
27
Q

Why reducing sugars primarily monosaccharides?

A

– oxidation rxn requires a FREE anomeric C for enzyme locate & interact carbonyl

28
Q

Reduction Modifications

A
    • reduction @ carbonyl C = ALDITOLS
    • Sorbitol reduced form glucose

**Reduced sugars can cause CATARACTS

29
Q

Amino Sugars

A
    • common branched polysaccharides (cell walls)
    • common addition to proteins (N-linked glycosylation)
    • N-linked glycosides

**OH replaced N of amino that’s attached to acetyl

30
Q

Methylation modifications

A

O-linked methylation
– same rxn mechanism monosaccharide polymerization but + non-sugar

– fucose = methylation is C-C linkage

31
Q

N-linked vs. O-linked glycosides:

A
    • N-linked glycosides = common branched carb structures, protein glycosylation, nucleosides (ribose + N-base bond)
    • O-linked glycosides = methylation, important TOXINS
32
Q

O-linked Glycosides

A

= some important toxins

– mech of methylation

33
Q

Essential Monosaccharides:

A 
D-glucose
D-galactose
D-Mannose
D-Xylose 
L-Fucose
N-Acetylgalactosamine (GalNAc) 
N-Acetylglucosamine (GlcNAc) 
N-Acetylneuraminic acid (Sialic acid) (NeuNAc)
34
Q

Maltose:

  • what 2 monosaccharides
  • C #’s from each participating
  • position of O-linked glycosidic bond
  • position anomeric OH monosaccharide
A

Maltose =

    • 2 alpha-D-glucose
    • 1 –> 4
    • alpha-glycosidic bond
35
Q

Sucrose

A
    • alpha-D-glucose –> beta-D-fructose
    • 1 –> 2
    • alpha-glycosidic bond
36
Q

Lactose

A
    • Beta D-galactose + D-glucose
    • 1 –> 4
    • beta-glycosidic bond
37
Q

Polysaccharide fxns:

A
    • glucose storage
    • structure
    • protein diversity
38
Q

List structural differences of blood type antigens

A

Type O (non-antigenic)
Type A + GalNAc
Type B + Gal

difference between A and B = N-linked acetyl

39
Q

Glucose storage structures

A
  • -Glycogen: 1–>6 linkages (branched); 1–>4 linear linkages
    • Amylose (unbranched) = Helical structure
40
Q

Structural polysaccharides

A
  • -Cellulose & chitin

- - commonly Beta-glycosidic bonds

41
Q

List protein residues with sides chains capable forming N- or O-glycosidic bonds (glycosylation)

A

Asn = N-linked

Ser and Thr = O-linked

42
Q

Glycoproteins

A
  • -Protein > Sugar (weight)
  • -membrane proteins (cell adhesion)
  • -soluble (cell signaling)
    • erythropoietin hormone + GlcNAc (E stores cel)
43
Q

Glycosaminoglycans

A
    • protein < sugar
    • repeating disaccharide structure
    • part of proteoglycans (huge ECM proteins-chondrotin sulfate, hyaluronic acid etc)
    • Heparin
44
Q

Mucins

A
    • protein < sugar
    • more complex structure pattern than glycosaminoglycans
    • Lubrication fxn: protection & hydration

Biochem Exam 2 (15 decks)

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