Tissue Architecture Flashcards
what is the function of the cytoskeleton at the sub cellular level?
organization, tensile strength, chromosome segregation, cell polarity, vesicular movement
what is the function of the cytoskeleton at the cellular level?
cell morphology/shape, motility, cell adhesion, division
what is the function of the cytoskeleton at the tissue level?
muscle contraction
what is the main component of microfilament?
actin 7nm
what is the main component of microtubules?
tubulin 25 nm
what is the main component of intermediate filaments?
lamin/cell specific proteins (8-12 nm)
what type of monomers make up microfilaments? what do they form?
g actin monomers
come together to form f actin (filamentous actin)
why is f actin unstable?
it is constantly undergoing addition (plus end) and removal (minus end) of g actin monomers
it has structural polarity
what is the main functions of microfilaments?
cell movement, locomotion, phagocytosis, cell division, contraction
how does f actin become more stable? (give specific examples)
becomes more stable by joining other proteins
accessory proteins, nucleating proteins, monomoer sequestering proteins, bundling proteins, side binding proteins
how do these proteins work with f actin?
accessory proteins nucleating proteins monomoer sequestering proteins bundling proteins side binding proteins
accessory proteins- stabilize, strengthen, cross link
nucleating proteins- stop monomer removal
monomoer sequestering proteins- semester monomers lol
bundling proteins
side binding proteins- stabilize and bind blocking sites for other proteins
what does phalloidin do?
bind and stabiles microfilaments
(death cap mushroom)
used in microscopy
what does cytochalasin do?
caps microfilaments plus end (no polymerization)
what does latrunculin do?
binds actin monomers and prevents polymerization
what are microtubule subunits and how do they work?
tubulin proteins - made of alpha and beta subunits
form heterodimers
heterodimers come together and form protofilaments
(polarity- heterodimers get added to the plus end of protofilaments )
how many protofilaments make up a microtubule
13
come together around a microtubule core
what is the main function of microtubules?
support shape of cell/organization
- cell organization: make tracks/roads for vesicles to move through
- cell division: interaction with mitotic spindle (extend from centrosome to chromosome)
- part of cilia and flagella in ciliated cells
how do drugs target microtubules in cancer cells?
microtubules targeted –> can’t pull apart chromatin in cell division –> cancer cells cant undergo cell division
how does taxol work?
binds to and stabilizes microtubules
how do colchicine and colcemid work?
binds tubulin dimers/ prevents polymerization
how do vinblastine and vincristine work?
binds tubulin dimers and prevents polymerization
What is the most important quality of Intermediate filaments?
rope like property that gives it high tensile strength (allows it to resist mechanical forces)
how do intermediate filaments form?
form coil coil proteins and accessory proteins that form bundles of filaments
(bring dimers and tetramers together)
what are the cytoplasmic elements that make intermediate filaments?
keratin filaments (epithelial cells)
vimentin (CT cells, muscle cells, glial cells)
neurofilaments (nerve cells)
*form based on the needs of the cell
what are the nuclear elements that make up intermediate filaments?
nuclear lamina (in all cells)
what is the function of nuclear lamina and where does it develop?
aids and stabilizes the nuclear membrane
a mesh like structure (of intermediate filaments) that forms adjacent to the nuclear envelope)
what is hutchinson Gilford progeria syndrome?
disease in the encoding of lamina A (nuclear lamina) (Intermediate Filament)
lose nuclear stability - leads to cellular instability - leads to accelerated aging
what are the main functions of the ECM/basal lamina?
anchor/engulf cells
maintain solid tissue (biochemical properties)
help define tissue boundaries
play role in cell polarity, survival, proliferation
inhibit or help cell migration
how do cells in the ECM interact with the basal lamina?
cell adhesion molecules
what makes up the ECM
tissue components secreted by nearby cells that aggregate into interlocking fibrous proteins/proteoglycans/adhesive matrix proteins
how is collagen made?
3 peptides made in the RER –> synthesized into pre-pro collagen–> turned into procollagen (trimer)–> alteration/processing in Golgi–> secreted into the ECM where it undergoes more processing
what processing can collagen undergo in the ECM?
cleavage of amino and carboxy terminals
collagen trimers form into fibers/sheets
what processing does collagen undergo in the ER?
hydroxylation of proline/lysine int he ER (before the trimer is formed)–> allows the proteins to form and stay stable
what is scurvy?
lack of ascorbate or iron (vit c deficiency)
vit c is an important cofactor for the hydroxylation of collagen
with hydroxylation - there is no folding/stability of trimeric collagen–> leads to unstable collagen which leads to the symptoms of scurvy
what are anchoring junctions?
attach cells to one another or to the ECM
keep cells together/ structural cohesion tissue
examples: adhering junction, desmosome, hemidesmosome
what are occluding junctions?
they create an impermeable/semi-permable barrier between adjoining epithelial cells
inhibit material transportation and control the movement of membrane transport proteins
what are gap junctions
link cytoplasm of adjacent cells to allow transport of molecules between adjacent cells
stretch across cell membrane
what are connexions?
make up gap junctions
interact and form complete gap channels
what are signal relaying junctions?
allow signals to be relayed across membranes (synapses)
what kind of interactions do cadherins have?
homophilic interaction on the extracellular side/ bind to actin on the intracellular side
what do all cell adhesion molecules have in common?
all ca2+ dependent glycoproteins
what kind kind of cell adhesion molecules make tight junctions?
cadherins
what are the types of cell adhesion molecules?
cadherins, interns, selections, Ig superfamily
what do integrins connect?
cell/ECM and cell/cell
connect cytoskeleton to ECM
what are integrins?
transmembrane cell adhesion molecules
what kind of interactions to integrins form?
interact with actin (intracellular) and fibronectin/collagen/laminin (extracellular)
what are the subunits of integrins?
alpha and beta subunits
B subunit determines integrin family
what type of cell adhesion molecules interact with RTK?
integrins
interact with RTK receptor on cell
initiate cell signaling cascade based on mechanical signal from outside the cell/ECM
what integrin subunit interacts with selectins? What is the pathway?
B2 integrins on monocytes – interact with selectins (e/p)
bind with ligand on selectins - localize white blood cells to the site during infection
how do selectins work during an infection?
inflammation/injury causes cytokines to be released –> this increases the amt of selectins on endothelial cells (on blood vessels)
these recruit WBC (with B2 integrins)
there is a low affinity interaction between WBC and selectins–> which causes the WBC to slow down/stop –> the WBC moves from blood into the tissue
what happens if there is a mutation in B2?
becomes difficult to fight infection (WBC can’t bind to selectin to slow down/stop)
what are the functions of the Ig superfamily as cell adhesion molecules?
expressed on endothelial cells
can bind to various leukocyte integration molecules (aid in immune response)
help with self recognition by immune cells
can take part in giving cell polarity
