Test 2: Carbohydrates

Front 1

What are the 3 ways of representing a carbohydrate?

Back 1

Fischer Projection

Haworth Projection

Chair Conformation

Front 2

What are the 2 major subgroups of isomers?

Back 2

Stereoisomers and constitutional isomers

Front 3

What are the 2 subgroups of a stereoisomer?

Back 3

1) Enantiomer

2) Diastereomer

Front 4

What's the difference between an enantiomer and a diastereomer?

Back 4

Enantiomers are nonsuperimposable mirror images while diastereomers are not mirror images at all

Front 5

What are the 2 subgroups of diastereomers?

Back 5

1) Epimers

2) Anomers

Front 6

What is an anomer and give an example

Back 6

An isomer that differ at a new asymmetric carbon atom after ring closure

Ex: alpha va beta D-glucose

Front 7

How does the stereochemistry of an enantiomer effect its interaction with an enzyme?

Back 7

Only one enantiomer will be a substrate for an enzyme, not both forms

Front 8

What are the 2 families of sugars based on structure and describe their structures?

Back 8

1) Aldoses have a terminal aldehyde group

2) Ketoses have an intrachain ketone group

Front 9

How do we distinguish between L and R isomers of in a fischer projection assuming that the methanol is at the bottom?

Back 9

Hydroxyl attached to chiral carbon that is farthest from the aldehyde/keto group is on the left for any L isomer or on the right for any D isomer

Front 10

How do we mathematically determine the possible number of isomers in a sugar?

How does this differ for a ketose and aldose?

Back 10

2^n where n = number of chiral centers

Ketose always has 1 less chiral center due to planar ketone

Front 11

What's the name for a 3, 4 ,5, and 6 carbon sugar?

Back 11

Triose, Tetrose, Pentose, and Hexose

Front 12

Describe the structure of Glyceraldehyde and draw it in its D form

Back 12

Triose Aldose

Front 13

Describe the structure of Erythrose and draw it in it's D form

Back 13

Tetrose Aldose with all the hydroxyls on the same side

Front 14

Describe the structure of Ribose and draw it in it's D form

Back 14

Pentose Aldose with all the hydroxyls on the same side

Front 15

Describe the structure of Arabinose and draw it in it's D form

Back 15

Pentose Aldose with the C2 hydroxyl being opposite of the rest

Front 16

Describe the structure of Xylose and draw it in it's D form

Back 16

Pentose Aldose with the C3 hydroxyl being opposite of the rest

Front 17

Describe the cyclization of Ribose and then draw it.

Back 17

It's a furanose (5 membered ring)

The carbonyl on C1 becomes an alcohol as the Hydroxyl on C4 becomes an ether, leaving the C5 methanol attached to the C4

Front 18

Describe the structure of Glucose and draw it in it's D form

Back 18

Aldose Hexose with the C3 hydroxyl on the opposite of the rest

Front 19

Describe the structure of Fructose and draw it in it's D form

Back 19

Ketone Hexose with the C3 hydroxyl being opposite of the rest and methanols on both terminals

Ketone on C2

Front 20

What's the relationship between Mannose, Glucose, and Galactose and describe their structural relationship

Back 20

Mannose and Galactose are epimers of glucose

Mannose is a C2 epimer

Galactose is a C4 epimer

Front 21

Describe the structure of Mannose and draw it in it's D form

Back 21

Aldose Hexose with C2 and C3 hydroxyls being opposite of C4 and C5 hydroxyls

Front 22

Describe the structure of Galactose and draw it in it's D form

Back 22

Aldose Hexose with C2 and C5 hydroxyls being opposite of C3 and C4 hydroxyls

Front 23

What is a hemiacetyl and what are the reactants in the reaction?

Back 23

Formed from an aldehyde and an alcohol

Front 24

What's the difference between pyran and furan?

Back 24

Pyran is a 6 membered ring while Furan is a aromatic 5 membered ring

Front 25

Pyranose can take 2 forms, how do they differ?

Include Haworth and Chair conformation in description

Back 25

The anomeric carbon's (C1) hydroxyl can be Up or Down on a Haworth or Axial/Equitorial for chairs

Front 26

When does a hemiacetal form?

Back 26

After the C5 OH attacks the C1 aldehyde groups carbonyl

Front 27

Why is the Beta-D anomeric form of glycopyranose predominate over the Alpha-D form?

Back 27

The Beta-D is more stable due to less steric hinderance between the C1 and C2 hydroxyls since they're oriented in opposite direction

Front 28

What's a hemiketal and under what conditions does it form?

Back 28

Forms after C5 OH attacks the C2 carbonyl Ketone

Front 29

What is the major heat-sensitive sugar in honey?

Back 29

Fructopyranose

Front 30

Hexose carbohydrates can exist in 2 conformation, what are they?

Back 30

Chair and Boat conformation

Front 31

How can copper aid in the detection of glucose?

Back 31

The aldehyde group in open chain glucose can reduce copper which results in a visible color change

Front 32

What glycosylated hemoglobin do we look for when identifying diabetics?

Back 32

Hemoglobin A1c

Front 33

How does hemoglobin A1c form?

Back 33

The open chain glucose's aldehyde group reacts with a hemoglobins amine group leading to a schiff base which rearranges to an Amadori product which is the hemoglobin A1c

Front 34

Glycosidic bonds form between the _____ carbon of a monosaccharide to ___, ____, and ____ atoms of other molecules

Back 34

Anomeric, N, S, O

Front 35

True or false:

Monosaccharides can be modified at other than the anomeric carbon?

Back 35

True

Front 36

What are the 3 common disaccharides discussed in lecture?

Back 36

Maltose, Lactose, and Sucrose

Front 37

Describe maltose

Back 37

Maltose is a repeating unit of amylose

Front 38

Which sugar discussed in lecture is "non-reducing?"

Back 38

Sucrose

Front 39

True or False:
Enzymes recognize the difference between alpha/beta linkages?

Back 39

True

Front 40

What is the main storage polysaccharide in plants and what are they composed of?

Back 40

Starch is a mixture of amylose (10-20%) and amylopectin (80-90%)

Front 41

Compare and contract the structure of amylose and amylopectin

Back 41

Amylopectin has an alpha-1,6 glucose branch every 30 residues

Both Amylose and Amylopectin have alpha-1,4 glucose links

Front 42

Describe the structure of the animal storage product glycogen.

Back 42

Glucose chains joined by alpha-1,4 links

Every 10 residues there's an alpha-1,6 residue

Front 43

Descrive the structure of the most abundant natural polymer in the world, cellulose

Back 43

Beta-1,4 D-glucose polymer

Front 44

What about cellulose's secondary structure makes it indigestible to animals?

Back 44

Hydrogen bonding allows for the formation of sheets which are harder to break down than helices

Front 45

What is it about glycogens structure that makes it better as a storage unit?

Back 45

The occasional (every 10 sugars) alpha-1,6 gives glycogen a less linear shape (more globular?) which provides more ends for rapid degradation compared to a straight chain

Front 46

What amino acids link to carbohydrates?

Back 46

Asparagine, Serine, and Threonine

Front 47

Compare and contract GlcNAc and GalNAc

Back 47

GlcNAc is C2 N-linked to an aspragine

GalNAc is C2 O-linked to a threonine

The C4 hydroxyl are opposite in each structure

Front 48

Compare the sugar content of glycoproteins to that of proteoglycans and to Mucins

Back 48

Glycoproteins are 1-10% carbohydrate at most

Proteoglycan are 80-95% carbohydrate

Mucins are also mostly carbohydrate

Front 49

Where are glycoproteins mostly found?

Back 49

Cell membrane proteins and secreted proteins

Front 50

What is the function of the carbohydate in a glycoprotein?

Back 50

Acts as a trafficking tag

Front 51

Where are proteoglycans mostly found?

Back 51

Structural components such as cartilage

Front 52

What is the predominant carbohydrate found in mucins?

Back 52

GalNAc

Front 53

Where are Mucins mostly found?

Back 53

Found in mucus and other lubricants

Front 54

What are the 6 functions of protein glycosylation discussed in lecture?

Back 54

1) To increase the complexity of the proteome

2) To direct trafficking

3) To direction folding (or lack of folding)

4) To contribute structural strength

5) To Provide protection against proteases

6) Involved in receptor binding

Front 55

In what part of the cell does glycosylation occur?

Back 55

ONLY in the ER Lumen and Golgi

NOT Cytoplasm

Front 56

What would prevent a glycosylated protein from being secreted?

Back 56

1) A mutation in a specific glycosyltransferase preventing it from getting to the ER

2) A mutation in the secretion apparatus that prevents all proteins from being secreted

Front 57

What do all N-linked sugars have in common?

Back 57

A (5) pentasaccharide core composed of 2 GlcNAc's and 3 Mannoses

All N-linked sugars can only bind to an Asn, if it's in the context of Asn-X-Thr or Asn-X-Ser where X cannot be proline

Front 58

What specialized lipid are N-linked oligosaccharides assembled on?

Back 58

Dolichol Phosphate

Front 59

What is the function of Dolichol Phosphate? How does GlcNAc play a role?

Back 59

Act as a scaffold that GlcNAc binds to first at which point a variety of sugars can be added

Front 60

Draw the structure of Dolichol Phosphate

Back 60

Front 61

How do we start a dolichol-phosphate oligosaccharide?

Back 61

GlCNAc-1-P Transferase adds UDP-GlcNAc at the expense of 1 phophate

Thus, the original dolichol phosphate is then bound to a GlCNAc phosphate

Product: Dolichol-P-P-GlcNAc

Front 62

What is the precursor used in the biosynthesis of oligosaccharides destined to become protein modification?

Back 62

UDP-glucose

Front 63

What enzyme do we use to transfer sugars?

Back 63

Glycosyltransferase

Front 64

What happens to a dolichol-phosphate oligosaccharide once it is completely assembled?

Back 64

It is tranferred to an Asn residue on the target protein that is to be glycosylated

Front 65

How is ABO blood type determined?

Back 65

It is determined by the presence of 2 extra glycosyltransferases on top of the enzyme needed to synthesize the O antigen since everyone has that

Front 66

What enzyme is responsible for the A antigen in blood types?

Back 66

GalNac transferase adds the extra N-acetylgalatosamine seen in people expressing A blood types

Front 67

What enzyme is responsible for the B antigen in blood types?

Back 67

Gal Transferase adds the extra galactose

Front 68

What do all blood types have in common?

Back 68

A O-antigen backbone composed of:

R - Galactose - Glucose - Galactose - Fucose

Front 69

Why do we have different blood types in the human gene pool?

Back 69

Pathogens mimic cell surface proteins as an evasion tactic. Having multiple glycosylation patterns makes it harder for them which increases our resistance

Front 70

Who is the universal donor and who is the universal acceptor?

Back 70

Universal Donor = O

Universal Acceptor = AB

Front 71

What is the function of Hyaluronan?

Back 71

To provide a backbone for aggrecan to bind through it's 1st globular domain

Front 72

What is a glycoconjugate?

Back 72

A polysaccharide linked to a protein or peptide

Front 73

What are the distinguishing compositional feature of Proteoglycans?

Back 73

It is composed of a few proteins lined with lots of glycosaminoglycans where at least 1 of the 2 sugars in the glycosaminoglycan unit are a negatively charged carboxylate or sulfate

Front 74

What is a glycosaminoglycan?

Back 74

A long unbranched polysaccharides consisting of a repeating disaccharide unit

Front 75

What is a heteropolysaccharide?

Back 75

A glycosaminoglycan complex carb. formed by combining a carb. with a non-carb. or carb-derivative group where at least 1 of the 2 sugars in the glycosaminoglycan unit are a negatively charged carboxylate or sulfate

Front 76

What examples of proteoglycans were discussed in lecture?

Back 76

Chondroitin 6-sulfate

Keratan Sulfate

Heparin

Front 77

What examples of Heteropolysaccharides were discussed in lecture?

Back 77

Dermatan Sulfate

Hyaluronate

Front 78

What allows for heteropolysaccharides and proteoglycans to exist in aqueous solution?

Back 78

Carboxyl groups, sulfates, or uronic acid

Front 79

Describe the structure of chitin and it's function

Back 79

It is a long polymer of GlcNAc mostly found in exoskeletons

Front 80

Describe the backbone and overall structure of a Mucin

Back 80

Backbone: It has VNTR's (Variable number tanden repeat regions) with a high degree of serine and threonine O-glycosylation through GalNAc

Overall highly branched and extended variable structure due to the high glycosylation

Front 81

What is the function of erythropoietin?

Back 81

It stimulates production of RBC's

Front 82

What is the purpose of glycosylating EPO?

Back 82

Glycosylation enhaces the stability of the protein in the blood

Front 83

What is the function of recombinant EPO in sports? How do we identify recombinant EPO?

Back 83

Recombinant EPO can be used to increase oxygen-carrying capacity in endurance athletes. Labs can identify recombinant EPO through isoelectric focusing to differentiate glycosylation patterns between native and recombinant EPO

Front 84

What are lectins?

Back 84

Proteins that bind to specfic oligosaccharides aka Glycan-binding proteins

Front 85

What are the 2 types of lectins discussed in lecture?

Back 85

L (lymph) lectin

C (calcium-requiring) lectin

Front 86

Where are L-lectins found and what is their proposed function?

Back 86

Found in leguminous plants and in the eukaryotic ER

maybe an insectiside in plants or chaperone protein in the ER

Front 87

What is unique about C-type lectins?

Back 87

They have a calcium binding domain that acts as a bridge between the protein and the sugar

Front 88

What protein in the C-type lectin family is involved in the inflammatory response? What does it do?

Back 88

Selectins bind immune-system cells to sites of injury in the inflammatory response

Front 89

What protein in the C-type lectin family is involved in reproduction?

Back 89

L-selectins are produced by embryos when they are ready to attach to the endometrium of the mothers uterus

Front 90

What are the 3 types of selectins and where do they bind?

Back 90

L (lympth carbs)

E (endothelial carbs )

P (Platelet carbs)

Front 91

What would prevent endothelial cells from adhering to leukocytes?

Back 91

1) Lack of calcium in the medium which inhibits C-type lectins

2) Glycosidases that cleave extracellular carb structures between neighboring cells

3) medium is hot?

Front 92

What occurs in I-cell disease at the molecular level?

Back 92

Lysosomes containg large inclusions of undigested glycosaminoglycans and glycolipids

Front 93

What causes I-cell disease?

Back 93

Improper M6P glycosylation of enzymes needed to degrade glycosaminoglycans and glycolipids

Enzymes are exported to blood and urine instead of the lysosome

Front 94

How does the influenza virus invade cells?

Back 94

Virus recognizes sialic acid residues linked to galactose on cell-surface glycoproteins

The virus binds via hemagglutinin and is endocytosed

Front 95

What is the function of Neuraminidase in the spread of the new influenza virions?

Back 95

To exit the cell, the virions binds to extracellular hemagglutinin. Neuraminidase then cleaves the glycosidic bond to the sialic residues and allows the virions to spread

Front 96

How do influenza medications work?

Back 96

Influenza medication inhibit the action of neuraminidase through transition-state analog inhibition which prevents spread of new virions

Front 97

What could be responsible for influenza resistance?

Back 97

1) Reduced extracellular sialic acid levels

2) Hemagglutinin binding antibodies

3) Neuraminidase-blocking activity

Front 98

What are the 2 ways to inhbit neuraminidase

Back 98

1) Transition state analog inhibition

2) Hydrolysis, phosphorylation, or glycosylation of neuraminidase

Front 99

What makes a sugar reducing vs non-reducing?

Back 99

An unbound anomeric carbon can exist in open-chain form, allowing for aldehydic activity. Non-reducing sugars are those that have both of their anomeric carbons bound and thus have no aldehydic activity