Ch 20 - Cell Connectors: Tissues, Stem Cells, and Cancer Flashcards
how do cells exist in the human body?
in tissues
what kind of tissue is blood considered?
connective tissue
plant cell walls are…
rigid
what makes up the extracellular matrix in animal tissues?
collagen
GAGs (glucoseaminoglycan)
what does collagen function in?
connective tissues
what anchors cells to the extracellular matrix (ECM)?
integrins
what do polysaccharides and proteins do?
they fill spaces and resist compression
what is the function of plant cell walls?
to provide support
what do plant cell walls lack?
lack of intermediate filaments
how do plant cells make up for their lack of intermediate filaments?
they rely on the cell wall to resist tearing forces
what is the plant cell wall composed of?
polysaccharides (lots of sugar) [Cellulose, Pectin]
what is cellulose?
rigid secondary walls
most abundant macromolecule in the biome
type of sugar found in mature plant cell walls
what is pectin?
composes primary cell wall of growing cells
gets converted to cellulose as plant grows and matures
where is cellulose synthesized?
on the outer surface of the cell
what is the cellulose synthase complex?
it synthesizes cellulose
how does the cellulose synthase complex move?
along microtubules
what anchors the cellulose synthase complex intracellularly?
microtubules
what are the four main types of animal tissues?
Epithelial
Muscle
Nervous
Connective
what is the function of epithelial tissue?
it forms boundaries
what is the function of muscle tissue?
contraction
what is the function of nervous tissue?
to send electrochemical signals to transmit info
what is the function of connective tissue?
form the ECM
how many types of collagen do mammalian cells contain?
over 20
what is the function of collagen?
to resist stretching
what is collagen?
large component of connective tissue
resist stretching
what is the structure of collagen?
rope-like
similar to intermediate filaments
how is collagen formed?
- *collagen molecules** self assemble to form a collagen fibril (a trimer)
- *collagen fibrils** group up to form collagen fibers
what is procollagen?
procollagen forms before collagen
self-assembles into collagen fibrils
what is the purpose of procollagen?
it prevents self-assembly of abundance of collagen fibers so the cell doesn’t fill with collagen
what is the process of procollagen to collagen fiber?
procollagen enters a secretory vesicle and is transported out of cell
the terminal procollagen extensions get cleaved off by procollagen proteinases to form collagen molecule
collagen molecule self-assembles into fibril
fibril assembles into fiber
how is a collagen molecule formed?
when the procollagen proteinases cleave the terminal extensions from the procollagen
what is Ehlers-Danlos syndrome?
genetic defect in collagen or procollagen proteinases
increases stretchiness of skin
what does collagen organization depend on?
the tissue it’s in
how is collagen organized in tendons?
parallel sheets
how is collagen organized in skin?
wicker-like pattern
why is the organization of collagen different in tendons and skin?
tendons only receive tension from one direction
skin can receive tension from multiple directions
what do fibroblasts do?
organize the fibers they secrete
bind
secrete matrix (with procollagen)
what causes stretch marks and wrinkles?
constant force and pushing on collagen causing it to break down or tear overtime
what does fibronectin do?
it binds to collagen fibers and the extracellular portion of integrin
changes confirmation of integrin protein
what is fibronectin?
an extracellular protein that binds collagen and integrin
what are integrins?
heterodimer transmembrane proteins that anchor cells to ECM
what binds to integrin extracellularly?
fibronectin
what binds integrins intracellularly?
actin or cytoskeletal elements
what does activation of integrin cause?
conformational change of integrin allowing it to bind to fibronectin and anchor collagen fibril to plasma membrane
what causes activation of integrin?
binding to ECM
what are glycosaminoglycans (GAGs)?
sugar type molecule present in ECM of certain elements like collagen that forms negatively charges chains of disaccharides
what do GAGs do?
resist compression
form chains
link to core proteins
what kind of chains do GAGs form?
hydrophilic negatively charged chains of repeating disaccharides that attract H2O
what to GAGs link to?
proteoglycans (core proteins)
what do proteoglycans form?
large aggregates
what are the functions of ECM molecules?
guide cell migration
influence cellular function
what are epithelial sheets?
multicellular sheets that form boundaries
what is the structure of epithelial sheets?
polarized (distinct top (apical) and bottom (basal))
anchored to basement membrane
what holds epithelia together?
junctions
what is the function of epithelia?
form boundaries
secretion
absorption
what is the basal lamina?
basement membrane
where cells anchor to connective tissue
what are epithelial anchored to?
basal lamina
how do you determine the type of epithelial sheet?
- How many layers?
- what shape are the cells?
what is a simple epithelial sheet?
it has one layer
what is a stratified epithelial sheet?
it has multiple layers
what is a columnar epithelial sheet?
rectangular cell
oval nucleus
what is a cuboidal epithelial sheet?
square/cube shaped cell
round nucleus
what is a squamous epithelial sheet?
flat/squished cell
flat nucleus
which surface of the epithelial sheet is free?
apical
which surface of the epithelial sheet is anchored?
basal lamina
connective tissue
what is primarily found in the basal lamina?
Type IV collagen
laminin
what are apical modifications a cell might have?
microvilli
cilia
what is cilia?
hair-like structures found on the apical surface of a cell
line the intestinal tract
what are microvilli?
___ structures found on the apical surface of epithelial sheets
what are some types of polarization a cell can have?
apical modifications
different cell types in a single tissue
what is an example of a single tissue with multiple cell types?
gut lumen
- absorptive cells (microvilli)
- goblet cells (secrete mucous)
what are the three types of cell junctions?
tight junctions
anchoring junctions
gap junctions
what is the function of tight junctions?
form water tight boundaries between cells
stitch plasma membranes together
what is the function of anchoring junctions?
anchor cells to cytoskeletal elements (other cells) and ECM
what is the function of gap junctions?
allow for intracellular communications
what is the importance of cell junctions?
they are crucial for maintenance of epithelial sheets and formation of boundaries
what proteins form tight junctions?
occludins
claudins
what anchoring junctions anchor cells to cells?
adherens junctions
desmosomes
what helps anchoring junctions anchor cells to basal lamina?
hemidesmosomes
what binds anchoring junctions intracellularly?
actin
what do adherens junctions and desmosomes utilize to form cell junctions?
cadherins
what are adherens junctions bound to intracellularly?
actin
what do cadherins do?
bind to each other
what type of bonding do cadherins use?
homotypic bonding
what does cadherin binding require?
calcium
what do bundles of adherens junctions do?
contract
aid in embryonic development
what do adherens junctions do during embryonic development?
aid in neural tube and eye cup formation
what happens if the neural tube fails to bind during embryonic development?
it causes spina bifida
what is the purpose of taking folic acid during pregnancy?
it can help close the neural tube and prevent spina bifida
what do desmosomes provide?
tensile strength
what do desmosomes anchor to intracellulary?
keratin filaments
what do adherens junctions and desmosomes anchor to intracellularly?
cytoskeletal elements (actin and intermediate filaments [specifically keratin])
what is a hemidesmosome?
junctions between cells and basal lamina
what do hemidesmosomes use to form junctions?
integrins
what do hemidesmosomes anchor to intracellularly?
keratin filaments
what do hemidesmosomes anchor to extracellularly?
basal lamina
what are focal adhesions?
junctions between cells and connective tissue
what are focal adhesions important to?
cellular migration
what do focal adhesions use to form junctions?
integrins
what do focal adhesions bind to intracellularly?
actin
what do focal adhesions bind to extracellularly?
connective tissue
what forms gap junctions?
connexons
what do gap junctions allow the passage of?
inorganic ions
water-soluble molecules
how do gap junctions work?
they open and close in response to various signals
what is the plasmodesmata?
plant cell version of gap junctions
allows communication between cells
what are the three types of GAGs?
chondroitin sulfate
keratan sulfate
hyaluronan
