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Biochem I final > Glycoconjugates > Flashcards

Glycoconjugates Flashcards

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)

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

A

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

19
Q

Proteoglycan functions (3)

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

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)

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?

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

Glycoproteins found where?

A

outer surface of plasma membrane, in ECM or in blood

24
Q

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

A

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

25
Q

How is CHO attached to protein? for glycoproteins. what bonds?

A

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
Q

Glycoproteins function?

A

CHO play role in protein-protein recognition

27
Q

What proportion of mammalian proteins are glycoproteins? vs bacteria and viral proteins

A
  • 50%
  • bacteria: only some glycosylate proteins
  • viral proteins: heavily glycosylated –> helps pathogens evade immune system
28
Q

Glycolipids?

A

lipids with covalently bound oligosaccharides (exposed to cell’s outer surface

29
Q

Glycolipids are components of what?

A

plant and animal cell membranes where head groups are oligossacharides

30
Q

Oligosaccharides in glycolipids can be recognized by ?

A

Lectins –> recognize sugar motif of glycolipids and glycoproteins

31
Q

2 functions of glycolipids

A
  1. nerve conduction and myelin formation
  2. signal transduction
32
Q

Glycoproteins function?

A

CHO play role in protein-protein recognition

33
Q

In vertebrae, ganglioside carbohydrate composition determines ?

A

blood groups

34
Q

in gram negative bacteria –> lipopolysaccharides cover the ? –> 3 regions

A

peptidoglycan layer
1. Lipid A region –> endotoxic
2. core region
3. O-specific chain region –> gives serotype and leads immune response from hosts

35
Q

Immune system identifies and targets specific species of bacteria by identifying species-specific ____________

A

lipopolysaccharides

36
Q

How to conduct analysis of glycoconjugates?

A

through mass spectrometry

37
Q

Extracellular matrix? gives (3) to tissues

A

material outside cell
- gives strength, elasticity and physical barriers to tissues

38
Q

Main components of ECM (3)

A
  • proteoglycan aggregates (aggrecan bound to hyaluronan)
  • collagen fibers
  • elastic/fibrous protein
39
Q

ECM and tumour cells relationship

A
  • ECM = barrier for tumours cells seeking to invade new tissues
  • some tumor cells secret heparinase that degrade ECM
40
Q

Some integral membrane protein are ___________ (type?) vs other integral membrane proteins are receptors for _______________ (type?)

A
  • proteoglycans (syndecans)
  • extracellular proteoglycans (integrins)
41
Q

proteoglycans link cellular cytoskeleton to ECM and transmit signals into cell to regulate (4)

A
  1. cell growth
  2. cell mobility
  3. apoptosis
  4. wound healing

Biochem I final (5 decks)

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