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MCD Cellular Organisation Of Tissue > 3 Extracellular Matrix Biology I > Flashcards

3 Extracellular Matrix Biology I Flashcards

1
Q

*Q: How is tissue organised? (use gut as example)

A

A: gut lumen

epithelial cells make the epithelium (highly folded)

connective tissue (between the two layers of epithelia) made of lots of ECM and few cells (inc fibroblasts)

smooth muscle (between two layers of fibroblasts) made of circular and longitudinal fibres

connective tissue

epithelia

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2
Q

Q: What is the extra cellular matrix? What components does it consist of? (2)

A

A: complex network of proteins and carbohydrates (filling spaces between cells)

both fibrillar and non-fibrillar components

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3
Q

*Q: What’s the function of the ECM? (5)

A

A: Provides physical Support

Determines the mechanical and physicochemical properties of the tissue

Influences the growth, adhesion and differentiation status of the cells with which it interacts.

Essential for development - tissue function and organogenesis

Molecules in the ECM can interact with receptors on cells. This interaction will influence the behaviour of cells.

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4
Q

Q: Give an example of a simple organism containing ECM.

A

A: Hydra vulgaris

made of two layers of cells (endoderm and ectoderm) with extracellular matrix (mesoglea) in the middle

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5
Q

*Q: What is connective tissue? What is it rich in? Which immune cell does it contain?

A

A: Extracellular Matrix + Component Cells (e.g. macrophages)

rich in extracellular matrix

macrophages

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6
Q

Q: What is the basal lamina?

A

A: separates epithelial cells from the underlying connective tissue

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7
Q

*Q: What components make connective tissue? (3)

A

A: Collagens

  • Type I, II and III (fibrillar)
  • Type IV (basement membrane)

Multi-Adhesive Glycoproteins

  • Fibronectin, Fibrinogen
  • Laminins (basement membrane)

Proteoglycans (ECM)

  • Aggrecan, Versican, Decorin
  • Perlecan (basement membrane)
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8
Q

Q: What do all ECMs contain?

A

A: some form of collagen

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9
Q

Q: What do matrix components interact with? What does this affect?

A

A: specific cell surface receptors

affects cellular behaviour

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10
Q

Q: What 3 components are only found in the basement membrane?

A

A: Collagen - Type IV

Multi-adhesive glycoproteins - Laminins

Proteoglycans - Perlecan

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11
Q

Q: What are the 4 types ECM abnormalities that result in human disorders?

A

A: Gene mutations affecting matrix proteins

Gene mutations affecting ECM catabolism

Fibrotic disorders due to excessive ECM deposition

Disorders due to excessive LOSS of ECM

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12
Q

Q: Name a human disorder due to excessive loss of ECM.

A

A: Osteoarthritis

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13
Q

Q: Name 3 fibrotic disorders due to excessive ECM deposition.

A

A: Cirrhosis

Kidney Fibrosis - diabetic nephropathy

Lung Fibrosis - silicosis

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14
Q

Q: Name 5 human disorders caused by gene mutations affecting matrix proteins. Include which matrix protein is affected.

A

A: Osteogenesis Imperfecta - Type I Collagen

Marfan’s Syndrome - Fibrillin 1

Alport’s Syndrome - Type IV Collagen (a5)

Epidermolysis Bullosa - Laminin 5 (in all 3 chains)

Congenital Muscular Dystrophy - Laminin 2 (a2 chain)

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15
Q

Q: Name 2 human disorders caused by gene mutations affecting ECM catabolism.

A

A: Hurler’s Syndrome - L-a-iduronidase

Other mucopolysaccharidoses - inability to degrade GAGs (glycosaminoglycans)

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16
Q

Q: How do you get disorders without affecting matrix proteins?

A

A: There can be mutations where matrix molecules aren’t affected but enzymes that are involved in MATRIX CATABOLISM are affected.

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17
Q

Q: What is fibrosis characterised by?

A

A: having too much matrix

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18
Q

*Q: Describe connective tissue in:

tendons and skin.

bone.

cartilage.

vitreous humour.

A

A: Tendons and Skin
-Tough and flexible

Bone
-Hard and dense

Cartilage
-Resilient and shock-absorbing

Vitreous Humour
-Soft and transparent

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19
Q

*Q: How do you get different connective tissues with different properties? (2)

A

A: composition of the extracellular matrix

Which collagens there are and how they assemble/interact/orientate

(determines physical and mechanical properties)

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20
Q

Q: What is the most abundant protein in mammals - 25% of total protein mass?

A

A: collagens (long and cable like structure)

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21
Q

*Q: What is collagen a major component of? (3)

A

A: bone, tendon and skin

long and cable like structure

22
Q

Q: What cell makes the extracellular matrix components?

A

A: fibroblasts

23
Q

Q: How are collagen fibrils aligned in skin? Same arrangement where? Tissues resist?

A

A: successive layers nearly at right angles to each other

same arrangement in mature bones and cornea

these tissues resist tensile force in directions

24
Q

Q: Collagens are a family of?

A

A: family of fibrous proteins found in all multicellular organisms

25
Q

*Q: What is each collagen molecules comprised of?

A

A: 3 alpha chains (polypeptide chains)= forming a triple helix

can be composed of one or more different alpha chains

26
Q

Q: Describe the structures of type I, II, and III collagen.

A

A: Type I collagen has chains from two different genes - its composition is [alpha1(I)]2 [alpha2(I)]

Types II and III collagen have only one chain type – their compositions are, therefore, [alpha1(II)]3 and [alpha1(III)]3

27
Q

Q: What does the alignment of the collagen fibrils determine?

A

A: which directions the tissue can resist tensile force in

28
Q

Q: What is the characteristic repeating pattern of collagen alpha chains? Why?

A

A: Characteristic repeat: gly-x-y : x is often proline and y is often hydroxyproline

Every third position must be a GLYCINE - this is the only amino acid small enough to occupy the interior of the triple helix.

29
Q

Q: In fibrillar collagens, each alpha chain is how many amino acids long? Forms?

A

A: ~1000

a left-handed helix

30
Q

Q: How do the 3 alpha chains of a collagen molecule interact?

A

A: Three alpha chains form a STIFF TRIPLE HELICAL STRUCTURE.

Each alpha chain forms a helix and each helix wraps around each other

31
Q

Q: Summarise how collagen assembles into fibres.

A

A: one alpha chain

Individual triple helices come together (associate laterally) to form FIBRILS

Fibrils come together (associate laterally) to form COLLAGEN FIBRES

32
Q

Q: Explain fibrillar collagen biosynthesis.

A

A: 1. synthesis of pro alpha chain

  1. hydroxylation of selected prolines and lysines
  2. glycosylation of selected hydrocylysines
  3. self assembly of 3 pro alpha chains
  4. procollagen triple helix formation in ER
  5. secretion -> exit cell
  6. cleavage of propeptides (from N and C regions)
  7. self assembly into fibril
  8. aggregation of collagen fibrils (cross linkages- covalently) to form a collagen fibre
33
Q

Q: How does the biosynthesis of fibrillar collagen differ to other types?

A

A: all newly synthesised collagen chain have non-collagenous domains at N- and C- terminals

these domains are removed after secretion in the case of fibrillar collagens but remain part of the collagen in most other types

34
Q

Q: Why is a hydroxyl group important?

A

A: contributes to interchain hydrogen bond formation

35
Q

Q: What do prolyl and lysl hydroxylases require? What does lack of lead to?

A

A: Fe2+ and vitamin C

lack of Vitamin C =underhydroxylated collagens which can’t aggregate together properly to form solid fibres - affects tissue stability (scurvy)

36
Q

Q: What does lysine and proline hydroxylation contribute to? What carries out this process?

A

A: hydrogen bond formation between chains (more stable)

prolyl and lysl hydroxylases

37
Q

Q: How are lysine and hydroxylysine further modified? When does this take place?

A

A: in the formation of covalent cross-linkages

only after the collagen has been secreted

38
Q

Q: What do covalent cross link provide? Which residues are involved? What does the type and extent of cross-links in tissue change due to?

A

A: tensile strength and stability

Lysine and hydroxy-lysine residues

age

39
Q

Q: What type of arrangement do collagen fibrils have? In skin? In tendons?

A

A: staggered

fibres run parallel but they cross in all directions - can resist tensile force in all directions.

Parallel Bundles - resist tensile force in one direction

you only get tensile strength in one plane

40
Q

Q: Which collagen does not form fibrils? How does it assemble? Essential to? Present where?

A

A: Type IV collagen (Network-Forming Collagen)

assembles into a sheet-like network - it is an essential component of basement membranes

  • N and C not cleaved off -> part of the mature molecule
  • forms dimers and tetramers when associate by C or N terminals

present in all basement membranes - molecular constitution varies from tissue to tissue

41
Q

Q: Which collagens are fibril-associated? (2)

A

A: Type IX + Type XII

42
Q

Q: Why are elastic fibres important? What are they made of? Rich in?

A

A: Important for the elasticity of tissues.

Important for the elasticity of skin, blood vessels and lungs.

Elastic Fibres = Elastin Core + Microfibrils (outer)

Microfibrils are rich in the protein FIBRILLIN

43
Q

Q: Often, collagen and elastic fibres are interwoven. What does this do?

A

A: limit the extent of stretching

44
Q

Q: What does the integrity of elastic fibres depend on?

A

A: microfibrils containing the protein fibrillin

45
Q

Q: What causes Marfan’s Syndrome? What do manifestations primarily involve? People with it tend to have? Predisposed to?

A

A: mutation in FIBRILLIN-1

skeletal, ocular and cardiovascular systems

arm-span which is longer than their height

Predisposed to aortic ruptures

46
Q

Q: What is elastin? Structure? Configuration?

A

A: protein consisting of two types of segments that alternate along the polypeptide chain.

Two types of segment: Hydrophobic regions and alpha-helical regions (rich in alanine and lysine)

many lysine side chains are covalently linked

Elastin is like a rubber band - it changes its configuration when stretched (individual molecules), when the stress is removed, it will return to its original configuration (random arrangement)

47
Q

Q: What are basement membranes also called? What are they? Main function? It’s not?

A

A: basal laminae

type of ECM: flexible thin mats of extracellular matrix underlying epithelial sheets and tubes

separate layers of cell from underlying tissue eg muscle and epithelia

not a cell membrane as does not contain phospholipids

48
Q

Q: What do basement membranes surround? What are they composed of?

A

A: muscle, peripheral nerves and fat cells and underlie most epithelia

highly specialised extracellular matrices containing distinct spectra of collagens, glycoproteins and proteoglycans

  • nidogen
  • perlecan
  • collagen IV (main)
  • laminin (main)
  • integren (receptors)
49
Q

Q: Give an example of a specific BM? Role?

A

A: GLOMERULUS - Basement membrane prevents macromolecules going from the blood into the nephron

50
Q

Q: What is Diabetic Nephropathy? Can lead to?

A

A: ECM accumulation - Impinging on capillaries and restricting renal filtration

=> RENAL FAILURE (can lead to)

51
Q

Q: What is Alport syndrome? Due to? Can lead to?

A

A: -disease of glomerulus

  • BM is abnormally split and laminated
  • not smooth or regular

due to mutations in collagen IV

=> progressive loss of kidney function and hearing loss

52
Q

Q: What are the major components of BM?

A

A: Collagen IV + Laminins

MCD Cellular Organisation Of Tissue (13 decks)

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