Exam 3 -- CB Flashcards
cytoskeleton
maintains cell architecture; allows movement of cells, and transport inside cells; three types: actin filaments, microtubules, intermediate filaments
Intermediate filaments
withstand mechanical stress; connects cells into tissues; allow cells to stretch without tearing; provide structure to the nucleus in animal cells
Microtubules
highways for intracellular active transport of vesicles, organelles, macromolecules; super dynamic (constant growing&shrinking) their polarity allows for directional transport; growth initiates at MTOC
Kinesin
plus end-directed motor protein that helps control transport on microtubule; stretches the ER along the microtubules like a net
dynein
minus end-directed motor protein that helps control transport on microtubules; pulls the Golgi towards the nucleus
Actin filaments
cortex stabilization; cell movement; muscle contraction; can be polymerized into a variety of useful shapes and structures; thin and flexible; grow in direction of cell movement
treadmilling
gain subunits at plus ends, lose subunits at the minus end (think actin filaments)
myosin
motor protein that moves along actin filaments; hydrolyzes ATP to fuel cycles of binding, release, rebinding; head domains binds actin, tail binds to cargo
Nuclear pore complexes
complex of different proteins that act as gates for letting molecules through nuclear envelope; proteins that line the central pore have extended unstructured regions that form a disordered meshwork
nuclear localization signals
sequences in a protein that bind receptors that direct proteins through the pore
GTPase switch
controls nuclear import/export; GTPase activates proteins (GAPs) which stimulates hydrolysis of GTP, guanine nucleotide exchange factors (GEF) exchange GDP for GTP
Ran GTPase
imposes directionality for nuclear transport
Immunoprecipitation
purification of a specific protein using antibody binding; combined with immunoblotting can detect protein-protein interactions
Endomembrane system
protein secretion system; nuclear envelope, ER, Golgi, early/late endosome, lysosome, transport vesicles, plasma membrane, cytosol
Endoplasmic reticulum
most extensive membrane system in a eukaryotic cell; processing of proteins; balances protein load with processing function
Signal recognition particle (SRP)
recognizes signal sequences for ER (hydrophobic amino acids); wraps around ribosome and binds near the catalytic site to pause translation
Glycosylation
covalent modification of a protein with oligosaccharides (usually short, branched chains of various sugars); protects proteins from degradation, serves as quality control checkpoint, targets the protein to a specific organelle, contributes to cell’s outer carbohydrate layer (plasma membrane proteins)
ER stress
imbalance between the load and capacity of ER
Unfolded Protein Response (UPR)
increase folding capacity & (temporarily) reduce load; either results in recovery and expansion of ER or apoptosis of cell
Golgi
sorts proteins; oligosaccharides attached to proteins; vesicles then take proteins to other parts of the cell (ER, lysosome via endosomes, plasma membrane, secretory vesicles); [FURTHER GLYCOSYLATION, SORTING]
constitutive secretion
replenishes plasma membrane lipids and proteins, allows cells to expand in size
regulated secretion
allows rapid release of specific proteins in response to a signal
Exocytosis
default pathway for proteins made at the Rough ER
endocytosis
process by which cells take in fluid, as well as large and small molecules, by invagination of the plasma membrane (how cells degrade and repurpose materials)
phagocytosis
invovels ingestions of large particles (or other cells/organisms) into large vesicles (done by specialized cells); used as defense mechanism by multicellular organisms
pinocytosis
involves ingestion of fluid and small molecules into small vesicles; involves large amounts of membrane getting removed (replaced by exocytosis); carried out by clathrin-coated vesicles
receptor-mediated endocytosis
similar to pinocytosis but involves specifically enriching which molecules are taken up
lysosome
degrade material from inside the cell
autophagy
damaged material/organelles/other large cellular components is encapsulated and fused with the lysosome for degradation; important in neurodegenerative diseases
ubiquitination
covalent addition of a small protein (ubiquitin) to a target protein; modification signals for degradation of the protein
proteasome
unfolds and degrades ubiquitinated proteins to generate single amino acids;
protein aggregation
large groupings of misfolded proteins; accumulate in cells and irreversible (think yoke of hard boiled egg); [can lead to problems and eventually neuro-degenerative diseases]; oligomer is most toxic
lysosome/Late endosome trafficking
regulated by UPR; kinesin takes aggregated protein connected to lysosome to periphery of cell for degradation
cytometry
used to study cell types in a population; forward scatter – cell size; side scatter – abundance/complexity
macroautophagy
degrades intracellular material (large)
endosomal microautophagy
alternative way to get into lysosome; formation of multi-vesicular bodies; depends on ESCRT proteins; engulfment by multi-vesicular bodies/late endosomes, fusion with lysosome, degradation
G1 phase
cell growth, performing functions, checks if environment is favorable before heading into S phase
S phase
DNA replication
G2 phase
organelles duplicated; checks for DNA damage; ensures all DNA was replicated; recover from replication and check
M phase
mitosis, cytokinesis
centrosome
provide framework for ensuring each cell gets the right complement of chromosomes; separates chromosomes during Mphase
mitotic spindle
duplicated set of centrosomes in cell that is starting to divide that work together to prep cell for division
cell cycle control system
triggers the major transitions in the cycle; highly conserved; works by turning on and off key components through phosphorylation; coordinated by cyclin-dependent kinases
cyclin/CDK inhibitor
regulates the cell cycle in response to DNA damage
p53
gene that regulates cell cycle; if there is too much DNA damage, p53 directs cell to apoptosis; tumor suppressor
S-Cdk
activated at end of G1; promotes full assembly and activation of the replication complexes; directs degradation of protein needed for initial assembly phase to avoid re-replication
M-Cdk
regulates M-phase
mitosis
chromosomes condensed into compact structures; chromosomes pulled apart; sister chromatids perfectly aligned in middle then pulled apart by mitotic spindles
cytokinesis
cell division and reorganization of everything into two cells; contractile ring of actin filaments and myosin motors contract and pinch off cells
necrosis
cell “explodes’; contents spilled out into extracellular space; leads to inflammation/immune response
apoptosis
programmed cell death; benefits organism by containing cell death and allows for cell to reuse amino acids, lipids, etc; prevents uncontrolled growth; regulated by stress pathways
caspases
cascade of proteases; kept inactive until they receive apoptosis signal
mechanism of apoptosis
initiator caspases cleave and activate other caspases, leading to a cascade of activation; irreversible – proteins broken down, golgi/ER/nucleus fragmentation, shut down of translatino
intrinsic signaling pathway
intiated inside cell; primarily result of DNA damage, oxidative damage, or other stresses; involves permeabolization of the mitochondrial membrane; ex. release of cytochrome c
extrinsic
initiated outside of cell; primarily result of developmental signals; initiated by receptor-ligand interactions at plasma membrane; does not involve permeabolization of mitochondrial membrane; ex. mobile ligands tha activate cascade of caspases
phosphatidylserine (PS)
Negatively-charged lipid that normally is only found on inner leaflet of the plasma membrane
annexin v
cell-impermeable fluorescent dye that binds to PS
