14 - Carbohydrates

Question 1

Isomer =

Answer 1

2 molecules same MOLECULAR formula

Question 2

What is constitutional isomer?

Answer 2

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!

Question 3

Aldose + Ketose

Answer 3

Tautomers

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

Question 4

where C # begin in carbohydrate structure?

Answer 4

starts terminal carbonyl C of aldose

Question 5

What are stereoisomers?

Answer 5

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

Question 6

2 main stereoisomers + major differences:

Answer 6

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

Question 7

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

Answer 7

1

– Both terminal C always Achiral

Question 8

Enantiomers

Answer 8

Mirror images @ ALL chiral centers

Question 9

Distereomers

Answer 9

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

4-C sugar:

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

Question 10

Fisher projection

Answer 10

– linear model of carbohydrate structure

structure

Question 11

Haworth Projection

Answer 11

– cyclical 2D representation carb structure

Question 12

Pyran ring

Answer 12

• • 6 member ring

- most 6-C carbs

Question 13

Furan

Answer 13

• 5 member ring

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

Question 14

What is anomeric C?

Answer 14

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

Question 15

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

Answer 15

CANNOT determine alpha/beta orientation of OH from Fisher projection

Question 16

alpha vs beta carbohydrate:

Answer 16

alpha carbohydrate – OH oriented DOWN

beta carbohydrate – OH = UP

Question 17

2 types of Distereomers:

Answer 17

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)

Question 18

Configurational isomers

Answer 18

differ order (spatial orientation) around chiral C

Question 19

conformational isomers

Answer 19

REVERSIBLE free rotation around single bond

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

Question 20

FURANose vs PYRANose conformational isomers

Answer 20

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

Question 21

C3H6O3 =

Answer 21

Trioses common structure

Question 22

C5H10O5 =

Answer 22

Pentose common structure

Question 23

C6H12O6 =

Answer 23

Hexoses common structure

Question 24

Fucose =

Answer 24

• • 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)

Question 25

Phosphorylation modifications

Answer 25

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

Question 26

Oxidation modifications

Answer 26

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

Question 27

Why reducing sugars primarily monosaccharides?

Answer 27

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

Question 28

Reduction Modifications

Answer 28

- - reduction @ carbonyl C = ALDITOLS - - Sorbitol reduced form glucose **Reduced sugars can cause CATARACTS

Question 29

Amino Sugars

Answer 29

- - 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

Question 30

Methylation modifications

Answer 30

O-linked methylation -- same rxn mechanism monosaccharide polymerization but + non-sugar -- fucose = methylation is C-C linkage

Question 31

N-linked vs. O-linked glycosides:

Answer 31

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

Question 32

O-linked Glycosides

Answer 32

= some important toxins | -- mech of methylation

Question 33

Essential Monosaccharides:

Answer 33

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

Question 34

Maltose: - what 2 monosaccharides - C #'s from each participating - position of O-linked glycosidic bond - position anomeric OH monosaccharide

Answer 34

Maltose = - - 2 alpha-D-glucose - - 1 --> 4 - - alpha-glycosidic bond

Question 35

Sucrose

Answer 35

- - alpha-D-glucose --> beta-D-fructose - - 1 --> 2 - - alpha-glycosidic bond

Question 36

Lactose

Answer 36

- - Beta D-galactose + D-glucose - - 1 --> 4 - - beta-glycosidic bond

Question 37

Polysaccharide fxns:

Answer 37

- - glucose storage - - structure - - protein diversity

Question 38

List structural differences of blood type antigens

Answer 38

Type O (non-antigenic) Type A + GalNAc Type B + Gal difference between A and B = N-linked acetyl

Question 39

Glucose storage structures

Answer 39

- -Glycogen: 1-->6 linkages (branched); 1-->4 linear linkages - - Amylose (unbranched) = Helical structure

Question 40

Structural polysaccharides

Answer 40

- -Cellulose & chitin | - - commonly Beta-glycosidic bonds

Question 41

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

Answer 41

Asn = N-linked | Ser and Thr = O-linked

Question 42

Glycoproteins

Answer 42

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

Question 43

Glycosaminoglycans

Answer 43

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

Question 44

Mucins

Answer 44

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