Tissue Architecture

Question 1

What are the 4 main characteristics of the cytoskeleton?

Answer 1

Dynamic
Adaptable
Stable
Strong

Question 2

How are cytoskeletal filaments dynamic and adaptable?

Answer 2

Switch between their small soluble subunits and large filamentous polymers

Adapt by when they receive a signal they RAPIDLY disassemble and subunits diffuse to new site and reassemble

Question 3

What property allow cytoskeletal filaments to be strong?

Answer 3

staggered long subunits= rope like properties
- less rigid because can twist and pull

Intermediate filaments do not have this characteristic

Question 4

What are Intermediate Filaments made of? What are their roles?

Answer 4

Lamin, often anchored to plasma membrane at cell- cell junctions

Tensile strength –> withstand mechanical stress
- rope like properties and stabilization through cross linking by accessory proteins

Form network and surround nucleus

Nuclear lamina= underlies and strengthens nuclear envelope

Question 5

What are the 2 classes of intermediate filaments?

Answer 5

Nuclear= nuclear lamins

Cytoplasmic= keratin filaments, vimentin (connective tissue), and neurofilaments

Question 6

How can progeria arise?

Answer 6

Mutation in intermediate filaments causing increased cellular aging

Question 7

What cytoskeletal filament is blistering of the skin associated with?

Answer 7

mutation in intermediate filament

Question 8

What are Microtubules made of? What are their roles?

Answer 8

alpha,beta-tubulin heterodimer= subunit
- long hollow polar tube (+ end for growth - end for disassembly, rapid process)

Mitotic spindle for chromosome separation
Cilia and flagella parts
Centrosome –> cell peripherally so tracks for transport

Question 9

What is the role of gamma-tubulin mircotubules?

Answer 9

Form nucleus that attaches to the (-) end of the microtubule serving as an anchoring point

Question 10

How does the drug Taxol effect microtubules?

Answer 10

Binds and stabilizes microtubules which prevent chromosomal segregation –> cells stalled in M phase –> apoptosis

Question 11

How do the drugs Cholchicine (colcemid) and Vinblastine (vincristine) effect microtubules?

Answer 11

stabilize monomers preventing polymerization –> slow cell division

Question 12

What are Microfilaments made of? What are their roles?

Answer 12

G-actin –> F-actin polymer, polarity

instability allows them to play role in cell movement

• locomotion, phagocytosis, cell division, contraction
• stabilize when associate with other proteins

Question 13

What is the action of the drug Phalloidin?

Answer 13

Bind and stabilize actin filaments

Use if eat death cap mushroom

Question 14

What is the function of collagen in the basal lamina and connective tissue? What is its composition

Answer 14

Main structural protein

Trimeric proteins (homo or hetero trimers) form collangeous triple helix 
- associate as fibers, sheets, or transmembrane structures

Question 15

What are the key steps of collagen synthesis?

Answer 15

1. In RER preprocollagen synthesized –> procollagen molecule inserted in to the lumen of the ER
2. Hydroxylation of proline and lysine residues, glycosylation of hydroxylysine residues
3. Self-assembly of tropocollagen molecule, initiated by disulfide bond formation in c-terminal extensions= Triple helix formed
4. Cleavage of propeptides, assembly into fibrils and fibers

Question 16

What is scurvy?

Answer 16

Loss of Cofactor= Ascorbate or Iron

Question 17

What is Ehlers-Danlos Syndrome?

Answer 17

Mutation in collage or collagen synthesis genes

• depending where mutation is in process there is different severity
• weakens connective tissue in the skin bones vessels and organs

Question 18

What is the difference between cell junctions and focal contacts?

Answer 18

Junctions= link to neighboring cells
Focal= link cells to ECM or basil lamina 

Both have roles in migration, immune system, tissue architecture, signaling pathways

Question 19

What are the 3 domains of CAMs?

Answer 19

Extracellular= binding to adjacent cell/matrix proteins

Transmembrane= links CAm to membrane

Cytoplasmic= to cytoplasm via linker porteins

Question 20

Is the Cadherin Superfamily Ca2+ dependent or independent? What are examples of classic and atypical cadherins?

Answer 20

Ca2+ Dependent

Classic= E (epithelial), N (neural), VE (vascular endothelial)
- linked to actin cytoskeleton, associated with adherens junctions

atypical= T and LI (liver intestine)
- homophilic adhesion proteins without interaction with catenins or link to actin cytoskeleton

Question 21

What is the role of Cadherins in cancer?

Answer 21

epithelial to mesenchymal transition

- E-cadherin decrease, N cadherin increase –> invasiveness and metastasis

Question 22

Is the Ig Superfamily Ca2+ dependent or independent? What are examples?

Answer 22

Independent

ICAM, VCAM, PECAM, NCAM
- recognition binding or adhesion processes of cells

Question 23

Is the Selectins Superfamily Ca2+ dependent or independent? What are examples and what are their roles?

Answer 23

Dependent

Bind to extracellular carbohydrates
Host defense mechanism
- allows for rolling during leukocyte adhesion cascade

E-selectin (endothelial), L-selectin (leukocyte), P-selectin (platelet)

Question 24

What is the role of Integrins?

Answer 24

Couple extracellular matrix to cell cytoskeleton

Activate signaling pathways

Cell-cell interactions via B2 family= on leukocytes allow for adhesion and transmigration to sites of infection

Question 25

What is the structure and function of anchoring junctions?

Answer 25

Attached to components of the extracellular matrix and anchored to one another
- keeps cells together and in the structural cohesion of tissues

Question 26

What is the structure and function of occluding junctions?

Answer 26

Tight junction

Prevent leakage of transported solutes and water and seals off body cavities from blood
- more strands less ions passed

Question 27

What is the structure and function of channel-forming junctions?

Answer 27

Gap junction

Directly connect the cytoplasm of two cells, which allows various molecules, ions and electrical impulses to directly pass through a regulated gate between cells

• composed of 2 connexons
• regulated by pH or Ca2+

Question 28

What is the structure and function of signal relaying?

Answer 28

Chemical synapses in nervous system