Extracellular Matrix

Question 1

secondary plant cell wall

Answer 1

• found in stronger structures (like tree trunks)
• has three layers with different orientations
• located in between the plasma membrane and primary wall

Question 2

cellulose

Answer 2

glucose monomers connected by B1-4 linkages

Question 3

cellulose synthase

Answer 3

polymerizing enzyme that moves within the plane of the plasma membrane along tracks of intracellular microtubules as cellulose is formed

Question 4

scurvy

Answer 4

caused by a lack of vitamin C (coenzyme ascorbic acid); vit. c is needed for the conversion of proline to hydroxyproline; without vit. c proline isn’t hydroxylated; collagen all over the body is affected

Question 5

lignin

Answer 5

modified phenols; lignin units bind in random ways and fills the space of the cell walls

Question 6

cellulose synthesis

Answer 6

• cellulose microfibrils synthesized on the exoplasmic face of the plasma membrane from UDP-glucose formed in the cytosol
• microtubules orient to guide S1, then rotate to guide S2, then S3 and guide the cellulose synthase

Question 7

hyaluronan

Answer 7

• 25,000 disaccharides, no sulfates, no protein
• repeats of glucuronic acid and glucosamine
• synthesized at the cell surface
• hydrophilic, can interact with water –> helpful in synovial fluid and cartilage

Question 8

largest “molecule” in the body

Answer 8

hyaluronin with proteoglycans; can include aggrecans of collagen

Question 9

fibronectin

Answer 9

• multiple binding regions
  
  • RGDS amino acid sequence binds to cell surface
• able to bind many components of ECM together; holds ECM together
• important role in cell migration/differentiation
• dimeric molecule

Question 10

glucosamine

Answer 10

component of synovial fluid, cartilage; make a great lubricant because it attracts water

Question 11

chondroitin sulfate

Answer 11

like hyaluronan but n < 250 and has sulfates

Question 12

structure of collagen

Answer 12

single peptide of collagen is helical (alpha-helix); three collagen peptides come together to make a triple helix

Question 13

glycosaminoglycans (GAGs)

Answer 13

variable group characterized by high carbohydrates

Question 14

another name for basal lamina

Answer 14

basement membrane

Question 15

integrins

Answer 15

• transmembrane surface receptor which binds fibronectin and/or laminin; binds cytoskeletal proteins on the cytosolic face
• binds amino acid sequence RGD on matrix proteins, such as fibronectin

Question 16

diseases involving deficient collagen synthesis

Answer 16

• Ehler’s-Danlos
• Osteogenesis Imperfecta
• Scurvy

Question 17

role of growth factors with ECM

Answer 17

• growth factors can be bound to ECM
• if the ECM gets damaged or disrupted, then the growth factors get released
• damage to ECM means damage to cell; release of growth factors allows repair response –> angiogenesis, epithelial cell proliferation etc.
• the ECM is a reservoir for growth factors

Question 18

composition of bone

Answer 18

proteoglycan/collagen network and calcium hydroxyapatite

Question 19

basal lamina

Answer 19

a sheet-like substrate for epithelial cells ; provides an important base to which epithelial and endothelial cells attach

Question 20

result of too much collagen

Answer 20

too much collagen laid down at wound site leads to tissue not being very stretchable

Question 21

collagen that predominates in the basal lamina

Answer 21

type IV collagen

Question 22

primary plant cell wall

Answer 22

extremely thin; cellulose oriented randomly and expands in all directions

Question 23

components of primary cell wall in plant cell (from PP photo)

Answer 23

• pectin
• cellulose
• microfibril
• hemicellulose

Question 24

laminin

Answer 24

• characterized by 3 proteins in a cross-link structure
• important feature: many binding sites and domains
  
  • binds to collagen, sulfated lipids, integrins, CHOs
• limited to the basal lamina
  
  • binds to other features of the ECM; helps onnect the overall structure

Question 25

two-component system of plant cell wall

Answer 25

1. cellulose fibers 2. lignin

Question 26

heparan sulfate

Answer 26

* able to bind FGF (fibroblast growth factors) * can bind chemokines on endothelial surface of vessels (WBC migration) * able to bind and activate ATIII (antithrombin III) to inhibit clotting

Question 27

Ehler's-Danlos Syndrome

Answer 27

rubber man syndrome; globular ends aren't correctly removed so collegen is poorly joined, causing weak joints; can lead to weaken blood vessels --\> aneurysms

Question 28

pectin

Answer 28

polymer of D-galacturonic acid and monosaccharides; modified sugars

Question 29

proteoglycans

Answer 29

* GAG linked to protein * 20 to 250 disaccharides; sulfates and proteins * glycolylation in ER/golgi * up to 95% CHO in proteoglycan

Question 30

most abundant protein in the body

Answer 30

collagen

Question 31

4 main classes of glycosaminoglycans (GAGs)

Answer 31

1. Hyaluronan 2. Chondroitin Sulfate 3. Heparan Sulfate 4. Keratan sulfate

Question 32

plasmodesmata

Answer 32

* this is what plant cell walls have instead of gap junctions * channels that connect the cytosol of a cell with that of an adjacent cell * gap large to allow entry of viruses

Question 33

synthesis of collagen

Answer 33

see page 2 ECM notes

Question 34

specific examples of problems involving too much collagen

Answer 34

**pulmonary fibrosis** -- difficulty with lung expansion **liver scar tissue** -- caused by excessive drinking; cyrosis of the liver leads to functional hepatocytes being replaced by collagen

Question 35

linus pauling

Answer 35

found that collagen has a triple helix

Question 36

Osteogenesis Imperfecta

Answer 36

brittle bone syndrome; glycine gets replaced with another amino acid which causes disruption in the helix --\> results in little or no helix formation; so deformed that the body detects it as foreign and degrades it, causing brittle bones

Question 37

pricipal structural components of basal lamina

Answer 37

collagen and laminin