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Flashcards in Extracellular Matrix Deck (45):
1

What is the ECM?

Filler and macromolecules (secreted by the cell)

2

Functions of ECM

1. Cellular division
2. Motility
3. Differentiation
4. Adhesion
5. Structure

3

3 classes of ECM components

1. Structural proteins
2. Proteoglycans
3. Adhesive glycoproteins

4

Examples and functions of structural proteins

Collagens and elastins → provide strength and flexibility

5

Proteoglycans

What are they:

Function:

Protein-polysaccharide complexes

Provide matrix for structural proteins

6

Examples and function of adhesive glycoproteins

Fibronectins and laminins → attach cells to matrix

7

______ is the most abundant protein in vertebrates and it contains __% of total body protein

Collagen → 25-30%

8

Tendons and ligaments contain a lot of?

Collagen

9

Collagen structure

Rigid triple helix of polypeptide chains

10

Collagen strength

1 mm fiber can hold 20 lbs

11

__ different alpha chains combine to form __ types of collagen

Which are most abundant?

25 different alpha chains → 15 types of collagen

I, II and III most abundant

12

Type I composes __% of collagen in body

90%

13

Collagen cross linking function

Strengthens collagen bundle to withstand high stress

14

Elastin provides flexibility to what tissues?

1. Lungs
2. Heart
3. Arteries
4. Skin
5. Intestines
6. Ears

15

Elasticity is dependent on what ratio?

Collagen : Elastin

16

Elastin composition

Proteins rich in glycine and proline (no hydroxylation) and elastin molecule (crosslinked between lysines)

17

Proteoglycan composition

Glycoprotein + glycosaminoglycan side chain

18

GAGs

Long polysaccharides → 2 monosaccharides in alternating order

19

Glycoprotein

Protein with GAGs (up to 95% carbohydrate)

20

How are proteoglycans classified?

And what are 3 of the most common?

By glycosaminoglycan side chain:

1. Chondroitin sulfate
2. Keratan sulfate
3. Heparin / heparin sulfate

21

Location of chondroitin sulfate

Cartilage (osteoarthritis implications)

22

Keratan sulfate locations and function

1. Cornea
2. Cartilage
3. Bone

Cushion

23

Proteoglycan functions

1. Receptors
2. Filtration
3. Shock absorption
4. Trap water (>50%x their weight)

24

Hyaluronate functions:

1. Lubricates joints
2. Found on surface of migrating cells → facilitates cell migration

25

Heparan sulfate

What is it:

Location:

Family with side chains made of D-glucosamine or L-iduronic acid

Found in every cell of body

26

Heparin

What is it:

Function:

One member of the heparan sulfate family

Anticoagulant

27

Heparan sulfate family functions (other than heparin)

1. Bind growth factors
2. Important role in inflammation
3. Entry of virus into cells (herpes, rabies)

28

Fibronectin

Most common adhesive glycoprotein (contains about 5% carbohydrates)

Family of closely related proteins

29

Fibronectin solubility

Can be soluble, insoluble or partialy soluble → caused by alternative splicing of the same gene

30

Fibronectin roles

1. Maintain cell shape
2. Possible role in cancer
3. Blood clotting (soluble form)
4. Wound healing → guides immune cells to wound
5. Cell migration

31

Laminins are mainly located where?

Basal laminae

32

Basal lamina

Separates ECM from epithelial cells

33

Basal lamina roles

1. Structural support
2. Permeability barrier (acts as filter in kidney)
3. Cell migration (may allow migration of cancer cells)

34

Matrix remodeling is most active at?

Sites of abundance-cellular sources:
1. Cartilage: chondrocytes
2. Bone: osteocytes, osteoblasts
3. Tendon: teniacytes (fibrocytes)
4. Cornea: fibrocytes

35

Enzymes which degrade ECM

1. Metalloproteinases
2. Serine proteases:

36

2 ways to stop ECM degradation

1. Tissue inhibitors of metalloproteinases (TIMP1, 2, 3, 4) → ireversible
2. Serine protease inhibitors

37

Polypeptide chains found in collagen are high in?

1. Glycine
2. Hydroxylysine
3. Hydroxyproline

38

Metalloproteinases

Specific for 1 ECM component

Requires zinc or calcium

39

Serine proteases

Cleave protein sequences at serine residues → work with metalloproteinases

40

Fibronectin's role in cancer

Carcinomas are unable to synthesize fibronectins → cell detaches from ECM

41

Type I collagen is found where?

1. Skin
2. Bones
3. Tendons
4. Ligaments

42

Collagen cross linking with aged animals

Can become abnormal → loss of joint function

43

2 forms of hyaluronate

Proteoglycan (backbone in cartilage) or free molecule

44

Basal lamina surrounds what types of cells?

1. Muscle
2. Fat
3. Schwann cells

45

Composition of basal lamina

Thin sheet (50 nm) of EC material