Exam 2

Question 1

What makes up the ECM?

Answer 1

glycoproteins (big proteins with small sugars)
proteoglycans (small proteins with big sugars)
elastic fibers

Question 2

Laminin

Answer 2

heterotrimeric complex that can bind to integrin

Question 3

Collagen

Answer 3

glycoprotein
provides tensile strength
binds to fibronectin
three types: fibrilllar, sheet forming, anchoring

Question 4

Fibrillar collagen

Answer 4

• glycoprotein found in bone, eye, tendons, dense CT
• made in the ER, Lys and Pro are hydroxylated, hydroxylysine is glycosylated, assembles into 3 alpha chains. Is then secreted into cell, the pro-domains are cleaved and fibrils are formed

Question 5

Sheet-forming collagen

Answer 5

glycoprotein found in the basal lamina

Question 6

Fibronectin

Answer 6

glycoprotein binds to collagen then to integrin

Question 7

Nidrogens

Answer 7

glycoprotein linker protein

Question 8

Perlecan

Answer 8

type of proteoglycan

Question 9

Aggrecan

Answer 9

proteoglycan found in the inside of cartilarge ECM
helps activate fibroblast growth factor
inhibits TGF-beta

Question 10

Syndecan

Answer 10

proteoglycan found embedded in the PM on fibroblasts

interacts with fibronectin

Question 11

Betacan

Answer 11

proteoglycan found embedded in the PM, helps activate TGF-beta signaling

Question 12

Elastic fibers

Answer 12

allow for stretching

found in ECM of CT, blood vessels, skin and lungs

Question 13

Elastin

Answer 13

type of elastic fiber that finds TGF-beta and prevents it from binding to receptor

Question 14

Microfibrils

Answer 14

polymers composed of fibrillin (mutated in Marfan’s)

Question 15

Matrix Metalloproteins

Answer 15

degrade ECM and require Ca and Zn

Question 16

Regulation of MMPs

Answer 16

1) local activation - secrete as inactive precursor
Ex. plasminogen -> cleaved to be plasmin which break up blood clots
2) confinement by cell surface receptors: inactive protease bind receptors and confine them
Ex. non-mutated uPA ninds to receptor and degrades the ECM, mutated uPA binds to the receptor and inhibits degradation (block cancer cells)
3) secretion of inhibitors: controlled by local MMPs
Ex. TIMP’s bind to active MMPs and inactivates it protecting the ECM

Question 17

Leukocyte extravasation

Answer 17

1) macrophage in damaged tissue releases cytokines to attract leukocytes
2) selectin expression induced on endothelial cells lining the blood vessel
3) carbohydrates on leukocytes weakly bind to selectins
4) integrins on leukocytes bind ICAM’s on endothelial cells
5) leukocytes pass through gaps mediated by PECAM’s

Question 18

Tight junctions (zonula occludens)

Answer 18

• located on the apical, lateral domain
• uses claudins and occludens that connect to actin
• forms a protective barrier that forces stuff to pass through the cell
• forms a functional barrier that maintains polarity

Question 19

Adherens junctions (zonula adherens)

Answer 19

• lateral domain
• cadherins and catenins that connect to actin
• hold the cell together by connecting to actin

Question 20

Desmosomes (macula adherens)

Answer 20

• lateral domain
• cadherins: desmoglein and desmocollins
• plaque made by plakoglobin and desmoplakin
• provide mechanical strength by linking plaques to intermediate filaments (keratin)

Question 21

Hemidesmosomes

Answer 21

• basal domain
• integrins (type IV and laminin)
• plaques made of dystonin and plecin
• attaches cell to basal lamina via keratin

Question 22

Gap junctions

Answer 22

• connects adjacent cells
• made of connexin (forms connexons)
• allows passage of small ions and electrical waves of excitation