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Tissues > Tissues 4 > Flashcards

Tissues 4 Flashcards

1
Q

Name 1 glycoprotein structure found everywhere in basal laminae.

A

Laminins (very large and multi-adhesive)

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2
Q

What are the 3 chains present in laminas?

A

Alpha, beta, gamma chains

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3
Q

Which cell surface receptors can laminins interact with?

A

Integrins

Dystroglycans

(amongst others)

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4
Q

Name some components of the basal lamina that Laminin can interact with.

A
  1. Type 4 collagen
  2. Nidogen
  3. Proteoglycans
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5
Q

What are chain mutations in laminin associated with?

A
  1. Muscular dystrophy

2. Epidermolysis Bullosa

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6
Q

What does the absence of the a2-chain in laminin 2(11) cause?

A

Congenital muscular dystrophy , presenting with hypotonia. general weakness and joint deformities.

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7
Q

What are fibronectins?

A

Glycoproteins

Present as either insoluble fibrillar network or soluble plasma protein.

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8
Q

Where are fibronectins found?

A

In body fluid or in ECM

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9
Q

How many genes derive fibronectin?

A

1 gene.

Variations in fibronectin arise from splicing the 1 gene.

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10
Q

Fibronectins are multi -…… and form …….?

A

Multiadhesive, form dimers,

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11
Q

Why are there no known variations of the fibronectin genes?

A

Functional fibronectin is crucial for viability.

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12
Q

How does fibronectin form a mechanical continuum with the actin cytoskeleton?

A

By binding with integrin on cell surface.

Integrin is transmembranous and associated with actin cytoskeleton

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13
Q

What is an RGD motif?

A

Sequence of aas.

Arg-Gly-Asp

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14
Q

What type of fibronectin produces an RGD motif recognised by integrin?

A

Type III Fibronectin

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15
Q

What is a proteoglycan?

A

Heavily glycosylated proteins.

Core protein associated with one or more Gycosaminoglycan chains (GAG) chains covalently attached.

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16
Q

What are GAG chains?

A
  1. Long, unbranched chains
  2. REPEATING DISACCHARIDES
  3. Huge volume relative to mass
  4. Hydrated gels resistant to compression
17
Q

Which proteoglycan family is found in the basement membrane?

A

Perlecan

18
Q

What proteoglycan family is involved in aggregating and is involved with hyaluronan?

A

Aggrecan

19
Q

Decorin?

A

Small, leucine rich proteoglycan family

20
Q

Cell surface proteoglycan family?

A

Syndecans 1-4

21
Q

In GAG chains, 1 out of 2 repeating sugars is always an amino sugar. T or F?

A

T.

22
Q

How do the proteoglycans attract water and become gels?

A

They are carboxylated and sulphated - and are highly negatively charged.

23
Q

What are the 4 main GAG chain groups?

A
  1. Hyaluronan
  2. Chondroitin sulfate and dermatan sulphate
  3. Heparan sulphate
  4. Keratan sulphate
24
Q

Hyaluronan. Describe.

A
  1. aka hyaluronic acid
  2. is simply a carbohydrate chain - no core protein
  3. synthesised at the cell surface, not ER or Golgi
  4. NOT SULPHATED
  5. HUGE - 1 molecule can have same volume as bacterium
  6. Consists of upto 25000 repeated disaccharides
  7. GAG and core protein linked by serine residue in core protein which binds to a link tetrasaccharide in GAG molecule
25
Q

Dermatan Sulphate structure. Describe.

A

Repeating disaccharides = iduronic acid and N-acetylgalactosamine-4-sulphate

26
Q

Chondroitin sulphate structure.

A

Repeating structures = glucuronic acid and N-acetylgalactosamine-4-sulphate

27
Q

Describe decorin.

A

Small proteoglycan that binds to collagen fibres and is essential for collagen fibre formation.

Lack of decor may result in fragile skin with reduced tensile strength.

Has only one dermatan sulphate molecule as a GAG side chain.

28
Q

Describe cartilage.

A

Network of proteoglycans with Type 2 collagen interwoven to form fibrils.

29
Q

Describe aggrecan.

A
  1. Major cartilage matrix constituent.
  2. Core protein with Chondroitin sulphate GAG chains on the end of the protein.
  3. Keratan sulphate GAG next to CS
  4. Hyaluronan next to keratan sulphate.
  5. Link protein binds hyaluronan to binding region.
30
Q

What does aggrecan form?

A

Supramolecular complexes.

31
Q

Describe how osteoporosis arises.

A
  1. Aggrecan GAGs highly sulphated, lots of carboxyl groups.
  2. Therefore, Multiple negative charges on aggrecan molecule.
  3. Therefore, cations attracted (e.g. Na), which are osmotically active.
  4. Lots of water retained, forming a gel.
  5. Water allows resistance to compressive forces.
  6. Osteoarthritis = excess loss of ECM. Painful and stiff joints and loss of gel.
32
Q

What degrades aggrecan?

A

Aggrecanase and metalloproteinases.

33
Q

What is liver cirrhosis?

A
  1. Fibrotic disorder

2. Excessive production of fibrous connective tissue in liver.

Tissues (11 decks)

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