L08 Flashcards
what are the types of animal tissue
epithelial
muscular
nervous
connective
what features do epithelial muscular and nervous tissues share
similar structure/make up
(high frequency of cell/cell contact
with limited cell/ECM contact)
what are the features of connective tissue
lower frequency of cell/cell contact
with higher frequency of cell/ECM contact
give examples for epithelial tissues
lining of gut or epidermal layer of skin
how are epithelial cells directly connected
thro cell junctions
what transmits mechanical forces from a cell to another
via cytoskeletal filaments
(actin/intermediate filaments)
what is the basal lamina
a thin layer of connective tissue comprising mostly of ECM that epithelial cells attach to
why are epithelial cells asymetrical/polarized
they have proteins at the basal end (connected to the basal lamina)
the apical end does not have these proteins
what are the types of epithelial tissues
columnar
cuboidal
squamous
stratified
(check slide 16 for the pictures)
how are epithelial cells indirectly connected
via ECM
what proteins are involved in epithelial cells contacting
intracellular adaptor proteins
transmembrane adhesion proteins
what are intracellular adaptor proteins attached to
cytoskeletal filaments
Name three reasons why cells form tissues
specialization and Division of Labor
Structural Integrity and Support
Intercellular Communication and Coordination
Name a specialized connective tissue
bone
what are the types of cell junctions found in epithelial (+ muscle + nervous) tissues
Adherens junctions: cadherin
Desmosomes
Tight junctions
Gap junctions
how are cadherin junctions maintained
via a cadherin molecule from each cell
what are cadherin molecules attached to
another cadherin (extracellular)
a linker protein (intracellular)
cadherin superfamily are Ca2+ dependent molecules
true
what are the classical members of the cadherin superfamily of Ca2+ dependent molecules
E-cadherin, N-cadherin, P-cadherin
cadherin binding is homophobic
FALSE
cadherin binding is Ca2+ dependent
TRUE
what does Ca 2+ binding do to cadherin molecules
Ca2+ binding prevents flexing so
promoting homophilic binding to
another cadherin
what happens when Ca 2+ is removed
cells dissociate from each other
how many extracellular domains does 1 cadherin molecule have
5
what separates the extracellular domains of cadherin molecules
flexible hinge regions
when are flexible hinge regions present
in the presence of Ca 2+
how does the Intracellular domain of cadherins interact with actin
via catenins and other adapter proteins
e.g. vinculin
what are the steps of macro assembly
membrane protrusions initiate cell-cell contact
actin and cadherin recruitment expands junction
actin remodeling and myosin recruitment expands the adherens junction
cell-cell connection leads to extending of microvilli
True
what are the features of Desmosomes junctions
similar to adherens junctions but contain specialized cadherins that connect with intermediate filaments, also
allow junctions to have strength
what happens in tight junctions
epithelial tissues act as a selective permeability barrier
differential transporter molecules are expressed in apical and basal plasma membranes to allow
selective transport
across epithelia
give an example of a transporter molecule involved in tight junctions
glucose transporters in small intestine
what are gap junctions
channels made from connexins and innexins
what are the features of gap junctions
small; wont allow macromolecule thro
Can be open or closed in response to signals
(e.g. dopamine reduces gap junction communications in certain neurons in retina)
what is the function of tight junctions
prevents leakage of extracellular molecules between cells
help polarize the cells
what is the function of adherens junctions
joins actin bundles between 2 cells
what is the function of desmosomes
join intermediate filaments between cells
what is the function of gap junctions
forms channels for small, water soluble molecules to pass from one cell to another
what proteins are involved in cadherin interactions
p120 catenin
beta catenin
alpha catenin
vinculin (binds alpha catenin to extend it)
what proteins are involved in desmosomes
plakoglobin and plakophilin (adaptor proteins)
desmoplakin (binds the intermediate filaments)
what proteins are involved in tight junctions
claudin and occludin
