Tissue Architecture Flashcards
What are the 4 main characteristics of the cytoskeleton?
Dynamic
Adaptable
Stable
Strong
How are cytoskeletal filaments dynamic and adaptable?
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
What property allow cytoskeletal filaments to be strong?
staggered long subunits= rope like properties
- less rigid because can twist and pull
Intermediate filaments do not have this characteristic
What are Intermediate Filaments made of? What are their roles?
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
What are the 2 classes of intermediate filaments?
Nuclear= nuclear lamins
Cytoplasmic= keratin filaments, vimentin (connective tissue), and neurofilaments
How can progeria arise?
Mutation in intermediate filaments causing increased cellular aging
What cytoskeletal filament is blistering of the skin associated with?
mutation in intermediate filament
What are Microtubules made of? What are their roles?
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
What is the role of gamma-tubulin mircotubules?
Form nucleus that attaches to the (-) end of the microtubule serving as an anchoring point
How does the drug Taxol effect microtubules?
Binds and stabilizes microtubules which prevent chromosomal segregation –> cells stalled in M phase –> apoptosis
How do the drugs Cholchicine (colcemid) and Vinblastine (vincristine) effect microtubules?
stabilize monomers preventing polymerization –> slow cell division
What are Microfilaments made of? What are their roles?
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
What is the action of the drug Phalloidin?
Bind and stabilize actin filaments
Use if eat death cap mushroom
What is the function of collagen in the basal lamina and connective tissue? What is its composition
Main structural protein
Trimeric proteins (homo or hetero trimers) form collangeous triple helix - associate as fibers, sheets, or transmembrane structures
What are the key steps of collagen synthesis?
- In RER preprocollagen synthesized –> procollagen molecule inserted in to the lumen of the ER
- Hydroxylation of proline and lysine residues, glycosylation of hydroxylysine residues
- Self-assembly of tropocollagen molecule, initiated by disulfide bond formation in c-terminal extensions= Triple helix formed
- Cleavage of propeptides, assembly into fibrils and fibers
What is scurvy?
Loss of Cofactor= Ascorbate or Iron
What is Ehlers-Danlos Syndrome?
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
What is the difference between cell junctions and focal contacts?
Junctions= link to neighboring cells Focal= link cells to ECM or basil lamina
Both have roles in migration, immune system, tissue architecture, signaling pathways
What are the 3 domains of CAMs?
Extracellular= binding to adjacent cell/matrix proteins
Transmembrane= links CAm to membrane
Cytoplasmic= to cytoplasm via linker porteins
Is the Cadherin Superfamily Ca2+ dependent or independent? What are examples of classic and atypical cadherins?
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
What is the role of Cadherins in cancer?
epithelial to mesenchymal transition
- E-cadherin decrease, N cadherin increase –> invasiveness and metastasis
Is the Ig Superfamily Ca2+ dependent or independent? What are examples?
Independent
ICAM, VCAM, PECAM, NCAM
- recognition binding or adhesion processes of cells
Is the Selectins Superfamily Ca2+ dependent or independent? What are examples and what are their roles?
Dependent
Bind to extracellular carbohydrates
Host defense mechanism
- allows for rolling during leukocyte adhesion cascade
E-selectin (endothelial), L-selectin (leukocyte), P-selectin (platelet)
What is the role of Integrins?
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
What is the structure and function of anchoring junctions?
Attached to components of the extracellular matrix and anchored to one another
- keeps cells together and in the structural cohesion of tissues
What is the structure and function of occluding junctions?
Tight junction
Prevent leakage of transported solutes and water and seals off body cavities from blood
- more strands less ions passed
What is the structure and function of channel-forming junctions?
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+
What is the structure and function of signal relaying?
Chemical synapses in nervous system
