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Biochem I final > Glycoconjugates > Flashcards

Glycoconjugates Flashcards

(41 cards)

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1
Q

Glycoconjugates?

A

Carbs covalently linked to other non-CHO biomolecules –> lipids and proteins

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2
Q

3 functions of glycoconjugates

A
  1. cell to cell communication and signaling
  2. labeling of proteins
  3. recognition sites for extracellular molecules
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3
Q

glycoconjugates commonly found on ? but also in ?

A

on exterior of plasma membrane but also intracellular

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4
Q

Glycosaminoglycans (GAG) structure? –> 2 monomers? some also contain ?

A

linear polymers of repeating disaccharide units
1st monomer: amino sugar: N-acetyl glucosamine/galactosamine
2nd monomer: negatively charged: uronic acid –> oxidized C6 OH into carboxylic group
- some also contain sulfate esters –> highly negative

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5
Q

GAG = extended hydrated molecule –> (increase or decrease) charge repulsion between inside of proteins

A

decrease

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6
Q

GAG can react with water –> role in ________ of ECM

A

viscosity

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7
Q

GAG forms meshwork with ________ proteins to form ________ –> plays role in (3)

A
  • fibrous proteins
  • extracellular matrix
  • connective tissue, cartilage and lubrification of joints
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8
Q

Hyaluronate: ? + repeated how many times? + found in (2)

A
  • no sulfate group!
  • 50 000x
  • articular cartilage and synovial fluid –> lubrification of ECM
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9
Q

Chondroitin-4-sulfate: repeated ? + found in?

A
  • 20-60x
  • cartilage around joints
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10
Q

Keratan sulfate: ? + repeated? + found in (3)

A
  • no sugar acid uronic acid (replaced by galactose)
  • 25 times
  • cornea, cartilage and bone
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11
Q

Herapin: repeated ? + contains ? + is an ?

A
  • 15-90x
  • iduronic acid and sometimes GlcA
  • Anticoagulant
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12
Q

Herapin (3) vs heparan sulfate (3)

A

herapin: in immune cells! more specific and more sulfated
heparan sulfate: heparin-like polysac but attached to proteins –> uniquitous –> less charged than heparin but same function!

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13
Q

Function of heparin/heparan sulfate (3)

A
  • prevent blood clotting by activating protease inhibitor antithrombin
  • bind to various cells regulates development and formation of blood vessels
  • can also bind to viruses and bacteria to decrease their virulence
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14
Q

Heparan sulfate interaction to form blood clot

A

negative charge of sulfates interacts with positive charge of thrombin (essential for coagulation) and antithrombin (inhibits thrombin in presence of heparan sulfate)

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15
Q

Proteoglycans: what? where?

A
  • rod-shaped protein “backbones” in cell membrane that are heavily glycosylated (covalently linked to GAGs)
  • on cell surface or in extracellular matrix (ECM)
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16
Q

How to GAG bind to extracellular proteins to form proteoglycans? VS how do proteoglycans bind to membrane proteins?

A
  • extracellular: through electrostatic interactions
  • membrane: covalently
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17
Q

Proteoglycan components (3)

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A
  • core protein (Ser-Gly-X-Gly)
  • tetrasaccharide bridge, linked to core protein from anomeric carbon of xylose (on bridge) to serine OH
  • GAGs linked to core protein via tetrasaccharide bridge
18
Q

Syndecan vs glypicans

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A

Syndecan: protein has single transmembrane domain –> integral membrane protein
Glypican: protein is anchored (GPI anchor) to lipid membrane

19
Q

Proteoglycan functions (3)

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A
  • interacts with variety of receptors from neighbouring cells and regulate cell growth
  • act on tissue organizers and influence various cell activities
  • bind to extracellular proteins through electrostatic interactions
20
Q

Proteoglycan aggregates? covers what surface? for 2 fct

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A
  • enormous supramolecular assemblies of many core proteins all bound to hyaluronan
  • covers joint surfaces –> articular cartilage: decrease friction and load balancing
21
Q

which 2 GAGS form huge noncovalent proteoglycan aggregates? –> fct (2)

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A

Hyaluronan and aggrecan: hold lots of water and provide lubrification

22
Q

Feather like shape: what is the long thing au millieu? then branche? then feuilles?

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A
  • middle = hyaluronan
  • branch = aggrecan core protein
  • GAG link chondroitin sulfate
23
Q

Glycoproteins found where?

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A

outer surface of plasma membrane, in ECM or in blood

24
Q

Glycoproteins have _____ (up to ?) ______________ joined covalently to _________

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A

one or more (up to 10-12) oligosaccharides joined covalently to protein

25
How is CHO attached to protein? for glycoproteins. what bonds?
anomeric C of CHO attached to aa of protein. - O-linked glycosidic bond: OH group of serine or threonine - N-linked glycosidic bond: amide N of asparagine
26
Glycoproteins function?
CHO play role in protein-protein recognition
27
What proportion of mammalian proteins are glycoproteins? vs bacteria and viral proteins
- 50% - bacteria: only some glycosylate proteins - viral proteins: heavily glycosylated --> helps pathogens evade immune system
28
Glycolipids?
lipids with covalently bound oligosaccharides (exposed to cell's outer surface
29
Glycolipids are components of what?
plant and animal cell membranes where head groups are oligossacharides
30
Oligosaccharides in glycolipids can be recognized by ?
Lectins --> recognize sugar motif of glycolipids and glycoproteins
31
2 functions of glycolipids
1. nerve conduction and myelin formation 2. signal transduction
32
Glycoproteins function?
CHO play role in protein-protein recognition
33
In vertebrae, ganglioside carbohydrate composition determines ?
blood groups
34
in gram negative bacteria --> lipopolysaccharides cover the ? --> 3 regions
peptidoglycan layer 1. Lipid A region --> endotoxic 2. core region 3. O-specific chain region --> gives serotype and leads immune response from hosts
35
Immune system identifies and targets specific species of bacteria by identifying species-specific ____________
lipopolysaccharides
36
How to conduct analysis of glycoconjugates?
through mass spectrometry
37
Extracellular matrix? gives (3) to tissues
material outside cell - gives strength, elasticity and physical barriers to tissues
38
Main components of ECM (3)
- proteoglycan aggregates (aggrecan bound to hyaluronan) - collagen fibers - elastic/fibrous protein
39
ECM and tumour cells relationship
- ECM = barrier for tumours cells seeking to invade new tissues - some tumor cells secret heparinase that degrade ECM
40
Some integral membrane protein are ___________ (type?) vs other integral membrane proteins are receptors for _______________ (type?)
- proteoglycans (syndecans) - extracellular proteoglycans (integrins)
41
proteoglycans link cellular cytoskeleton to ECM and transmit signals into cell to regulate (4)
1. cell growth 2. cell mobility 3. apoptosis 4. wound healing

Biochem I final (5 decks)

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