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Cell Biology > Extracellular matrix > Flashcards

Extracellular matrix Flashcards

1
Q

What is the ECM?

A

Any substance produced by cells & secreted into the extracellular space within the tissues

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2
Q

Why is the ECM important?

A

> structural - provides physical support for cells & a linkage between cells/tissues

> cell mobility - forms a substrate on which cells can move & provides cues that guide direction of movement

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3
Q

Describe the structure of connective tissue

A

Scattered cells e.g. fibroblasts

Predominantly ECM

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4
Q

Describe the composition of ECM in connective tissues

A

Collagen fibres cross-linked by accessory proteins in a matrix of proteoglycans

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5
Q

What are proteoglycans?

A

Proteins bound to polysaccharides

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6
Q

Describe the structure of epithelial tissues

A

Layers of cells bound closely to form protective sheets

Minimal ECM

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7
Q

Describe ECM in epithelial tissues

A

concentrated under epithelia (basal lamina)

- provides base for cells to sit on & acts as molecular sieve & substrate for migrating cells

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8
Q

Describe the composition of ECM in plants

A

Cellulose fibres cross-linked w/ hemicellulose in matrix of highly branched polysaccharides

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9
Q

Describe how ECM is arranged in plants

A

All plant cells surrounded by ECM

= cell wall

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10
Q

What are cellulose fibres analogous to?

A

Collagen fibres

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11
Q

How does the ECM differ between plants & animals?

A

Plant ECM contain polysaccharide fibres

Animal ECM contains fibres made of protein
- collagen & elastin

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12
Q

What is the function of collagen?

A

Resists tensile force

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13
Q

How many different collagen genes are there in mammals?

A

42

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14
Q

How are collagen fibres formed?

A
  1. 3 single-stranded collagens cross-link
    = collagen fibrils
  2. Collagen fibrils link to form collagen fibres
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15
Q

In what orientation are collagen fibres organised?

A

In 2 orthogonal directions

= 90 degrees to each other

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16
Q

Give an example of a fibril forming collagen

A

Type II collagen

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17
Q

Give an example of a cross-linking collagen

A

Type IX collagen

- has a kink in molecule so can bind along the side of 2 fibres at diff angles

18
Q

What is the function of elastin?

A

Provides tissues with elasticity

19
Q

What is elastin composed of?

A

Large filaments w/ lots of random spring-like coils

20
Q

What is elastin cross-linked by?

A

Lysine

Hydroxylysines

21
Q

How is the ECM in plants similar to in animals?

A

Matrix consists of polysaccharides

Plants: pectin (forms hydrated gel)

Animals: glycosaminoglycans = GAGS
(e.g. hyaluronan)

22
Q

What are the features of GAGS?

A

> highly -ve charge
hydrophilic
linked to proteoglycans

23
Q

Why is a -ve charge in GAGS significant?

A 
Carboxyl group creates
 -ve charge
--> attracts water
= swells up 
= cushioning affect
24
Q

What is GAGS made up of?

A

Repeating disaccharides of glucoronic OR iduronic acid
+
N-acetylglucosamine OR N-acetylgalactosamine

25
Q

What is formed when GAGS chains are covalently linked to proteins?

A

Proteoglycans

26
Q

What is there variation in that enables many types of connective tissue?

A

> relative proportion of fibres to cells in ECM
no. & proportion of diff cell types in ECM
proportion & arrangement of fibres in ECM
composition of non-ferrous component of ECM

27
Q

What are the 3 main cell types?

A

Fibroblasts
Macrophages
Mast cells

28
Q

What are the 4 specialised cell types?

A

> osteocytes (bone)
chondrocytes (cartilage)
adipocytes (adipose/fat)
blood cells

29
Q

What was different in the ‘rubber skin man’?

A

Collagen not properly assembled
- doesn’t resist tensile force
(Elastin = good as skin springs back to normal)

30
Q

What were the 2 possible causes of the ‘rubber skin man’s’ condition?

A

Failure of conversion of lysine to hydroxylysine by lysol hydroxylase
OR
failure to cleave off propeptide termini

–> fibrils & fibres don’t form

31
Q

Which cell type is found in areolar connective tissue?

What fibre types are found in the tissue?

A

Fibroblast

Elastin
Collagen

32
Q

What cell type is found in adipose tissue?

Which fibre type is found in the tissue?

A

Adipocytes

Reticular fibres

33
Q

Which cell type is found in tendons & ligaments?

Which fibre type is found in the tissue?

How are the fibres orientated?

A

Fibroblast

Collagen

Parallel orientation along the line of force

34
Q

Which cell type is found dermis of skin & organ joint capsules?

Which fibre type is found in the tissues?

A

Fibroblast

Collagen

35
Q

Which cell type is found in elastic cartilage?

Which fibre type is found in the tissue?

A

Chondrocyte in lacuna

Elastin

36
Q

Which cell type is found in bone?

A

Osteocytes in lacuna

37
Q

Give examples of conditions where there are defects in the ECM

A

Scurvy

Fibrodysplasia ossificans progressiva

38
Q

What are the causes of scurvy?

A

Vitamin C deficiency

–> defective collagen synthesis

39
Q

Why is Vit C essential for collagen synthesis?

A

Vit C = cofactor for propyl hydroxylase
–> forms hydroxyproline
= stabilises triple stranded collagen

40
Q

What are the symptoms of Scurvy?

A

Skin fragility & bleeding
Tooth loss

(Due to lack of normal fibrils)

41
Q

What does Fibrodysplasia ossificans progressiva cause?

A

Muscle & connective tissue (e.g. tendons) gradually replaced by bone

Cell Biology (23 decks)

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