Bio Test 4b Flashcards
jobs of the cytoskeleton
- adopts variety of cell shapes
- organize components in cytoplasm
- interact mechanically with environment
- carry out coordinated movement
the three types of filaments
- intermediate filament
- microtubules
- action filament
microtubules
25 nm in diameter
actin filament
7 nm in diameter
functions of intermediate filament
- provide muscle cells and skin epithelial tissues with great strength
- also stretch along the length of nerve cell axons
- keeps cells connected, allows them to not lose contents
structure of intermediate filaments
- 10 nm in diameter
- subunits are fibrous proteins with N-terminal globular head, C-terminal globular tail and central elongated alpha-helical rod domain
- coiled-doil dimer to tetramer to 8 tetramers twisted into rope-like filament
tissue
an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function
what are the four types of tissues
- connective
- epithelial
- nervous
- muscular
connective tissue
such as bone and blood
epithelial tissue
layers of cells that cover organ surfaces
nervous tissue
central nervous system and peripheral nervous system
muscular tissue
provides contractility
the five types of cell junctions
- tight junction
- adherens junction
- desmosome
- gap junction
- hemidesmosome
tight junction
- connect plasma membrane of adjacent cells, typically epithelials, in sheet partition plasma membranes (apical vs basal)
- form barriers to protect organs
adherens junction
- links actins of adjacent cells
- key connecting proteins called cadherins
desmosome
links intermediate filaments, keratin
gap junction
protein channels, made of connexins which form into a 6 subunit formation called conexon
hemidesmosome
anchors cells to ECM through integrin
extracellular matrix
- collagen is one of major components
- other components include: laminin, fibronectin, gelatin
- mutations usually cause skin blisters
tumor
- solid lesion formed by an abnormal growth of cells called neoplasm
- usually caused by multiple mutations in somatic cell
characteristics of metastatic cancer cells
- change cell junctions
- break loose
- epithelial-mesenchyme transition (EMT)
- degrade extracellular matrix
- metastasize
oncogens
- promoting growth in normal situation
- cause cancer when hyperactive (gof or dominant mutation)
tumor suppressor genes
- provide growth check in normal situations
- cause cancer when inactive (lof or recessive mutation)
hyperactive
creation of oncogenes by mutations of proto-oncogene or DNA abnormalities
multiple-hit
model for cancer formation
tumor size
- 10^8: visible on x-ray
- 10^9: palpable
- 10^12: cause death in the paitent
What is the doubling time of a typical breast tumor?
100 days
what is Gleevec
new type of anti-cancer drug that inhibits oncogenic kinase(s)
multiple-hit in colon cancer
- mutation in APC gene (tumor suppressor gene) causes neoplasm
- mutation in ras gene (oncogene) causes small tumor
- mutation in other tumor suppressors cause large tumor
- mutation in p53 gene (tumor suppressor gene) causes metastatic
at what rate are nerve cells renewed?
zero
at what rate are intestinal cells renewed?
every few days
at what rate are red blood cells replenished by our bone marrow?
120 days
at what rate is bone tissue renewed?
10 years
at what rate are skin cells renewed?
2 months
stem cells
undifferentiated cell that can continue dividing indefinitely, generating daughter cells that undergo terminal differentiation into particular cell types
- undifferentiated
- able to self renew
- small number
- slow dividing
- specialized in adult tissues
types of stem cells
- embryonic stem cells
- adult stem cells
- induced pluripotent stem cells or iPS
- cancer stem cells
totipotent
capable of giving rise to any cell type or complete embryo
pluripotent
capable of giving rise to many different cell types
multipotent
capable of giving rise to limited set of cell types
embryonic stem cell
- taken from inner cell mass of early embryo at blastocyst stage
- can be maintained in culture almost indefinitely
- can differentiate into many cell types depending on growth factors and hormones
types of adult stem cells
- soted in particular niches
- intestinal stem cells
- epidermal stem cells
- hemopoietic(hematopoietic) stem cells in the bone marrow
- hair follicle stem cells
intestinal stem cells
- types of adult stem cell
- lie near bottom of crypt
- slow dividing, cycle time: >24 hrs.
- producing rapid dividing progenitor cells, cycle time: ~12 hrs
hair follicle stem cell
- type of adult stem cell
- wnt signaling induces stem cell proliferation by inhibiting APC
- found in the bulge
epidermal stem cells
- type of adult stem cell
- st basal layer adherent to basal lamina
hemopoietic or hematopoietic stem cell
- type of adult stem cell
- found in bone marrow
- can divide and differentiate into many different cell types
induced pluripotent stem cell
- use differentiated cells from adult
- introduce three key genes: Sox-2, Oct-4 and c-Myc
- differentiated stem cells return to undifferentiated and pluripotent status, iPS
- iPS then can differentiate into many different cell types
cancer stem cell
- express cell surface markers that are associated with stem-like cells
- share at least two features with normal stem cells: self-renewal and multilineage differentiation potential
- comprise around 0.1-10% of cancer cell population
- display high activity of signal cascades that define stem cells (Wnt)
- more resistant to common therapy than differentiated tumor cells
