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MSA > Zachara_glycobiology > Flashcards

Zachara_glycobiology Flashcards

1
Q

what are three essential properties of glycans

A

They are hydrophilic, hydrated, and often negatively charged

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2
Q

name three glycoconjugates in vertebrates

A

glycoproteins, glycolipids, and proteoglycans

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3
Q

what are 9 most common monosaccharide building blocks

A

glucose, galactose, GalNAc, GlcNAc, mannose, fucose, xylose, sialic acid, GlcA, IdoA

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4
Q

two other names for carbohydrates

A

glycans, sugars

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5
Q

a non-carbohydrate moiety

A

aglycone, covalently linked to the glycone

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6
Q

humans use glycolipids built exclusively on…

A

sphingosine, aka glycophingolipids

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7
Q

glycosaminoglycans

A

long repeating charged disaccharides that when linked to proteins become proteoglycans

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8
Q

a glycosaminoglycan that is rarely found bound to proteins

A

hyaluronan

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9
Q

a protein covalently modified by 1+ carbs

A

glycoprotein

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10
Q

glycocalyx

A

dense, sugary coat of cells/tissues

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11
Q

3 key roles of surface glycoproteins

A

cell adhesion, self/non-self recognition, pathogen invasion

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12
Q

the carbon in sugars which undergoes nucleophilic attack to become circularized

A

carbon 1 , or the anomeric carbon

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13
Q

T/F. All common monosaccharides in vertebrates have the same chirality - dextrarotatory (D) configuration

A

True

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14
Q

3 common modifications of sugar hydroxyl groups

A

sulfate, phosphate, or acetyl groups

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15
Q

difference between glucose and galactose

A

one single position of a bond at carbon 4

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16
Q

name 4 features which contribute to polysaccharide diversity

A

linear vs branched structure, alpha or beta configuration of anomeric carbon, aglycone attachment, and linkage position of each monomer to the next sugar

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17
Q

where do monosaccharides come from (3)

A

diet, salvage from degraded glycans, or derived from other sugars

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18
Q

two classes of sugar transporters

A

facilitated diffusion (GLUT) and energy dependent

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19
Q

how are carbohydrates added to nucleotides

A

through high energy phosphate bond, generate ATP analog. typical conjugation partners are UDP-, GDP-, and CDP

20
Q

where are glycoconjugates synthesized

A

ER and golgi, sugar nucleotides pulled in from the cytoplasm by transporters

21
Q

class of enzymes which catalize glycoconjugation

A

glycosyltransferases

22
Q

these two residues terminate most glycoprotein and glycolipid glycons

A

fucose and sialic acid

23
Q

influenza surface proteins and their connection to glycans

A

hemagglutinin, initiates flu infection by binding to cell-surface sialic acids to keep newly made virus from sticking to it, neuraminidase removes sialic acids on soluble mucins that would prevent cell-surface binding of invading virus

24
Q

how does a cell get rid of unwanted extracellular glycoproteins and proteoglycans (2)

A

either shed from cell surface, or internalized and degraded in the lysosome

25
Q

how are glycosphingolipids classed?

A

based on first sugar added to sphingosine - either galactose or glucose

26
Q

two ways glycolipids mediate cell-cell interactions

A

either through binding to complementary molecules on opposing plasma membranes (trans) or modulating activities of proteins in same plasma membrane (cis)

27
Q

myelin

A

insulator that allows for rapid nerve conduction

28
Q

N-linked glycans

A

glycan linked to protein through an amide bond to an asparagine residue

29
Q

sequence motif of N-linked glycan

A

Asn-Xaa-Ser/Thr (Xaa is any AA but proline)

30
Q

O-linked glycans

A

glycan linked to protein through hydroxyl on serine/threonine residues (but also sometimes proline, lysine or tyrosine)

31
Q

GPI anchors

A

lipid linked to protein through glycan intermediate, way to anchor proteins to the plasma membrane

32
Q

N-glycan core sugar sequence

A

Man3GlcNAc2Asn

33
Q

three types of N-glycans

A

oligomannose, complex, hybrid

34
Q

14-sugar glycan transferred to proteins during translation

A

precurser dolichol phosphate

35
Q

mucin-type o-glycans

A

shield epithelial surfaces from physical/chemical damage and protect against pathogen infections. huge proteins, more than 50% sugar by weight. attract water and form gels

36
Q

congenital muscular dystrophies linked to mutations in this biosynthetic pathway

A

O-mannosylation- mannose modification of certain proteins improves their solubility and trafficking to cell surface (ex alpha-dystroglycan, glycoprotein connecting ECM to cytoskeleton in many tissues)

37
Q

two functions of glycan binding proteins

A

mediating cell adhesion and regulating signaling

38
Q

two groups of GBPs

A

lectins and glycosaminoglycan binding proteins

39
Q

selectin role in inflammation and injury

A

injury increases expression of selectins, which slow down leukocyte circulation and mediate rolling and chemotaxis into tissue to migrate towards the site of injury

40
Q

A, B, O blood type antigens formed by…

A

sequential action of glycosyltransferases encoded by 3 loci

41
Q

how is O-GlcNac different than other forms of protein glycosylation

A

it is adding in an O-linked fashion, but is not further extended - it is instead dynamically added and removed from proteins like how protein phosphorylation is

42
Q

how is O-GlcNac thought to regulate proteins

A

can compete with phosphorylation, regulation analagous to phosphorylation regulation

43
Q

T/F. Glycans dominate cell surfaces

A

Totally true

44
Q

how do proteins recognize glycans? (5)

A

h-bonding, salt-bridges, hydrophobic stacking, calcium coordination, multivalency

45
Q

how does heparin anticoagulant work

A

thrombin cleaves fibrinogen to soluble fibrin, which starts to stick together. thrombin then becomes inhibited by antithrombin protease. heparin binds to antithrombin, accelerating inhibition and blocking coagulation

46
Q

5 forms of protein glycosylation

A

N-linked, O-linked, GPI-anchors, C-mannosylation, and phosphoglycosylation

47
Q

4 ways glycans can change a glycoconjugate

A

alter structure, localization, turnover, and interactions

MSA (13 decks)

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