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POM > ECM > Flashcards

ECM Flashcards

1
Q
  • What is the ECM?
A

Complex network of proteins and carbohydrates

Comprises of fibrillar and non-fibrillar components
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2
Q
  • What does fibrillar mean?
A

Fibre-making

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3
Q
  • What are the key functions of the ECM?
A

Provides physical support

Determines mechanical and physiochemical properties of tissue

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

Essential for development, organogenesis and tissue function
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4
Q
  • Where is the ECM?

- What is the ECM made of?

A

Spaces between cells

Collagens - e.g Type I, II, III (fibrillar) and Type IV (basement membrane)

Multi-adhesive glycoproteins

Proteoglycans
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5
Q
  • What properties do connective tissues in the tendon and skin have?
  • What properties do connective tissues in the bone have?
  • What properties do connective tissues in the cartilage have?
A

Tough and Flexible

Hard and Dense

Resilient and Shock-absorbing
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6
Q
  • Give an example of a fibrotic disorder due to excessive ECM deposition
  • Give an example of a disorder due to excessive loss of ECM
A

Liver Fibrosis - cirrhosis
Kidney fibrosis - diabetic nephropathy
Lung fibrosis - idiopathic pulmonary fibrosis (IPF)

Osteoarthritis
cushioning properties of cartilage over the ends of bones are lost
aggrecan is cleaved by metalloproteinases and aggrecanases
loss of aggrecan fragments to synovial fluid

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7
Q
  • How is collagen arranged in skin, mature bone and cornea and how does this relate to its function?
A

Successive layers nearly at right angles to one another

This resists tensile force in all directions
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8
Q
  • Describe the structure of collagen

- What is the difference between a heterotrimer and a homotrimer?

A

3 alpha chains
Forming a triple helix

Heterotrimer is collagen with more than one type of alpha chain
Homotrimer is collagen with 3 of the same alpha chains
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9
Q
  • Describe the structure of an alpha chain
A

gly-x-y repeat

Glycine

X is often Proline

Y is often hydroxyproline

Each alpha chain is around 1000 amino acids long forming a left-handed helix
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10
Q
  • Explain the biosynthesis of fibrillar collagen
A
  1. Occurs in Fibroblast
    1. Synthesis of pro-alpha chain
    2. Post-translational modifications - Hydroxylation of prolines and lysines and glycosylation of hydroxylysines
    3. Self-assembly of 3 pro-alpha chains
    4. Procollagen triple helix formation
    5. Secretion
    6. Cleavage of propeptides
    7. Self assembly into fibrils
    8. Aggregations of collagen fibrils to form a collagen fiber
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11
Q
  • Which compounds are involved in the cross-linking of collagen?
  • How are hydrogen bonds formed between collagen molecules?
A

Lysine
Hydroxy-lysine

Prolyl and Lysyl Hydroxylases use Fe2+ and Vitamin C as co-factors to form hydroxylysine and hydroxyproline

Allowing them to form hydrogen bonds with one another
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12
Q
  • What happens therefore, if there is a Vitamin C deficiency And what is this condition called?
A

Underhydroxylated collagens, so there are dramatic consequences for tissue stability

Scurvy
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13
Q
  • What is Ehlers-Danlos Syndrome (EDS)
A

Group of inherited connective tissue disorders whose symptoms include fragile (stretchy) skin, blood vessels and loose joints

Negatively affecting collagen production, structure and processing
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14
Q
  • What property does Collagen type IV have that promotes its function?
A

Uncleaved N and C termini allow it to interact with other Collagen molecules to form a network of collagen

Allows it to act as a basement membrane
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15
Q
  • What is basement membrane (BM)?
  • Where is BM found?
  • what mutation is Alports syndrome associated with
A

Flexible, thin mats of extracellular matrix underlying epithelial sheets and tubes
Highly specialised ECM containing a distinct combination of collagen, glycoproteins and proteoglycans

Surround muscle, peripheral nerve and fat cells
Underlie most epithelia

mutation in type 4 collagen (alpha 5 chain)

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16
Q
  • What are Diabetic Nephropathy?

- What is Alport Syndrome?

A

Highly thickened BM which restricts renal filtration leading to renal failure

Mutations in Collagen IV result in abnormally split and laminated GBM, associated with progressive kidney function loss and hearing loss
17
Q
  • What are elastic fibres made of?

- What condition are mutations in the protein fibrillin-1 associated with?

A

Core of protein elastin
Microfibrils - rich in the protein fibrillin

Marfan's syndrome - Spider-like fingers, tall and thin, long legs, arms, fingers, toes. overly flexible joints and scoliosis
18
Q
  • What is elastin composed of?
A

2 types of segment that alternate along polypeptide chain:

Hydrophobic region

Alpha-helical regions rich in alanine and lysine (lysine chains are covalently cross linked)
19
Q
  • Describe the structure of Laminins?

- What makes Laminins multi-adhesive properties?

A

They are heterotrimeric proteins made up of an alpha-chain, beta chain and a gamma-chain
Forming cross chained molecules

They are multi adhesive proteins that can interact with a variety of cell surface receptors including integrins and dystroglycan
20
Q
  • What group of tissues tend to be affected by mutations of genes coding for Laminins?
  • What causes congenital muscular dystrophy and what are the symptoms?
  • what causes epidermolysis bullosa
A

Muscular

Alpha-2 chain in Laminin2
Hypotonia (abnormally decreased muscle tension), generalised weakness and deformities of the joints

mutation in all three chains of laminin 5

21
Q
  • What 2 forms can fibronectins exist as?

- Explain the multi-domain structure of fibronectin

A

Insoluble fibrillar matrix
Soluble plasma matrix

Several domains are linked by disulphide bonds
Fibronectin then has several collagen binding sites and cell binding sites
22
Q
  • How is fibronectin involved in the binding of collagen fiber to actin filament?
A

Fibronectin binds to collagen fiber and the integrin receptor on the other side which provides linkage between matrix and cytoskeleton

Adaptor protein binds to other end of integrin

Actin filament binds to adaptor protein
23
Q
  • What are proteoglycans?
A

Core proteins covalently attached to one or more glycosaminoglycan (GAG) chains

24
Q
  • What are the 4 proteoglycan families grouped upon their structural and functional characteristics
A

Basement membrane proteoglycans: e.g. perlecan

Aggregating proteoglycans (interact with hyaluronan): e.g. aggrecan

Small leucine-rich proteoglycans: e.g. decorin

Cell-surface proteoglycans: e.g. syndecans 1-4
25
Q
  • What are the functions of fibronectin?
A

Regulating cell adhesion and Migration in a variety of processes e.g. - embryogenesis and Tissue repair

Important in wound healing to promote blood clotting

26
Q
  • What are GAGs made of and what charge are they usually?
A

Repeating disaccharide units with one or two of these sugars being an amino sugar

Negative as they are sulfated or carboxylated
27
Q
  • What are the 4 main groups of GAGs according to the disaccharide repeating unit?
A

Hyaluronan

Chondroitin sulfate and dermatan sulfate

Heparan Sulfate

Keratan Sulfate
28
Q
  • What makes hyaluronan distinct from other GAGs?

- Where is hyaluronan found in high viscousity?

A

Simply a carbohydrate chain without a core protein

Vitreous humour of the eye
In synovial fluids of joints
29
Q
  • Why do hyaluronan chains tend to occupy a relatively large volume?
A

Hyaluronan can undergo a very high degree of polymerisation

30
Q
  • How does Aggrecan’s presence lead to large quantities of water being retained by the environment it is in?
A

GAGs are highly sulfated, increasing negative charge

Also present are large numbers of negatively charged carboxyl groups

Multiple negative charges attract osmotically active Na+ ions
31
Q
  • How is aggrecan perfectly suited to resist compressive forces in cartilage matrix?
A

Under compressive load, water is given up but is regained once the load is reduced

Suited to resist compressive forces
32
Q

what are the functions of elastin and collagen and how do they work together

A

elastin- important for elasticity of tissues eg skin, blood vessels and lungs
collagen is important for tensile strength of tissues

they are woven together to limit the extent of stretching

33
Q

what do fibril associated collagens do and give examples

A

associate with fibrillar components
regulate organisation of collagen fibrils

types 9 and 12

POM (47 decks)

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