Cell Exam 3
You want to design a drug that can relax both skeletal and smooth muscles. Which of the following proteins could be a target?
Voltage gated Ca2+ channel, voltage gated Na+ channel, ca2+ pump
which of the following compounds can not be a potential anti-cancer drug? a compound that blocks association of Ras-GEF w/ RTK, a compound that inhibits Ras-GAP, a compound that inhibits Ras-GEF, a compund that inhibits MAPKKK
A compound that inhibits Ras-GAP
To design a drug that can inhibit insulin secretion, which protein should not be chosen as the target? tubulin, kinesin, dyenin, or clathrin
Dyenin
activated myosin-11 cause
MLCK phosphorylates myosin light-chains
MT, AF, IF subunit, size and shape
MT: 25 nm, alpha/beta tubulin-dimer AF: 8nm , actin monomer IF: 10 nm, IF proteins
MT, AF, IF assembly and polarity
MT: GTP-dependent assembly, polar AF: ATP- dependent assembly, polar IF: multilevel assembly
MT, AF, IF associating proteins
MT: kinesin, dynein AF: myosin 1 and 2, filamin, ARP complex, cadherin, integrin, Rho family, tropomyosin, troponin IF: cadherin and integrin
During a drug screen you find a compound that can block the binding of Ca2+ to troponin. Predict the effect of this drug. A. Muscle spasm B. Muscle paralysis C. Hypnosis D. No effect
Muscle Paralysis
classic pathway of cell signaling
extracellular signal molecule > receptor > intracellular signaling molecules > target proteins > cell response (fate or behavior)
T/F: To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol
false
t/f a receptor found by only one type of signal molecule can mediate only one kind of cell response
false
t/f about intermediate filaments, they are made of globular subunits
false
t/f activated g protein produces 3 separate subunits that function independently
false
t/f all cells will respond to the endocrine signals as endocrine molecules are broadcast throughout the body
false
t/f each type of receptor must induce an independent signaling pathway and avoid interference with other intracellular signaling pathways
false
gap junction
forms channels that allow small, intracellular, water-soluble molecules, including inorganic ions and metabolites, to pass from cell to cell
4 signal molecules
gas, steroid, derivative from aa, protein
endocrine signal
global- in bloodstream, hormone released in blood
GTP tubulin
growing MT
Growth factor signaling pathway
growth factor > RTK > PI3K > AKT > BAD/BCl2 ( cell survival) OR AKT > mTOR (cell growth)
Cell movement involves the coordination of many events in the cell. Which of the following phenomena is NOT required for cell motility?
influx of Ca2+ into the cytoplasm
the members of the steroid hormone receptor family
interact with signal molecules that diffuse through the plasma memrbane
motor proteins
intracellular transport
adherens junction
joins an actin bundle in one cell to a similar bundle in a neighboring cell
desmosome
joins the intermediate filaments in one cell to those in a neighbor
To design a drug that can inhibit LDL uptake, which protein should not be chosen as a target? tubulin, kinesin, dyenin, or clathrin
kinesin
paracrine signal
local- effect adjacent cells
general functions of cytoskeleton
mechanical support, maintain cells shape, interacts with specialized proteins called motor molecules
Which of the following would you expect to see in a cell that has been exposed to colchicine?
mis-organized endomembrane system
lamin related disease (intergrin)
misregulation of the genome causing progeria
Which of the following proteins can move cargos through an actin filament?
myosin
nuclear intermediate filaments
nuclear lamins in all animal cells
causes of depolarization
open ACh gated cation channel
cause of calcium flooding
open calcium release channel on SR
cause of calcium influx
open voltage gated calcium channel on t-tubule
causes of firing action potential
open voltage gated sodium channels
step 1 (prometaphase)
phosphorylation of lamin and nuclear pore proteins > disassembly
Ca2+ release, causes what to occur with t-tubules
plasma membrane extend inward, surrounding each myofibril, allowing action potential to spread inward of muscle fiber
what determines the directions of MT growth and cargo transport
polarity, + end: beta, - end: alpha
3 assembly models for intracellular signaling complex
preassembly on ascaffold, assembly on activated receptor, assembly on docking sites on membrane
RHO
promotes actin filament bundling and contraction
Rac
promotes actin polymerization
CDC42
promotes protrusion of filapodia
fast response to signal
protein regulation: fast, short term
molecular switch
rapid on and off, phosphorylation and gtp coupled
ACh receptor and action
receptor: GPCR action: excitatory neurotransmitter at many nerve muscle synapses and in cNS
adrenaline receptor and action
receptor: GPCR action: increases BP, Heart rate and metabolism
insulin receptor and action
receptor: IR (type of RTK) Action: stimulate glucose uptake, protein synthesis and lipid synthesis in various cell types
cortisol receptor and action
receptor: adrenal gland action: affects metabolism of proteins, carbon and lipids in most tissues
Wnt receptor and action
receptor: frizzled family action: cell proliferation
ethylene receptors and actions
receptor: on ER membrane action: gene TF on, fruit ripening
delta receptor and actions
receptor: prospective neurons, various other developing cell types action: inhibits neighboring cells from becoming specialized in same way as the signaling cells
growth factor receptors and actions
receptors: RTK action: control cell survival and growth
troponin
regulates the position of tropomyosin, ca2+ binding
synaptic signal
release neurotransmitter in neuron
tight junctions
seals neighboring cells together in an epithelial sheet to prevent leakage of molecules between them, helps polarize them
autocrine signal
self- target on same cell
GDP tubulin
shrinking MT
contact dependent signal
signal molecule not released, transmembrane protein
mechanical signals
signal transduction
3 mechanism models of intracellular signaling pathways
signaling complex, second messenger, molecular switch
second messenger
small size- large amount, rapid diffusion. cAMP, DAG, IP3, Ca2+
IF functions
strengthen (desmosome), lamin (chromatin organization/regulation)
AF functions
support, transport (myosin 1), cell migration (steps, key proteins, regulator: Rho-GTPase), muscle contraction, skeletal muscle fiber structure, Ca2+ signaling
nuclear lamina and nuclear skeleton/matrix
supports nuclear envelope and chromatin organization
which of the following happens when a G-protein coupled receptor activates a G protein?
the alpha subunit exchanges it bound GDP to GTP
5 types of cell junctions in epithelia
tight junctions, adherens junctions, desmosome, gap junction, hemidesmosome
function of intracellular signaling complex
to enhance the specify and efficiency of signaling, the best strategy is to localize signaling proteins in the same part of the cell
slow response to signal
transcriptional response: slow, long term
MT functions
transport (vesicles) and organization (er/golgi), mitosis, cilia/flagella (dyenin, ATP)
t/f about intermediate filaments, each filament is about 10 nm in diameter
true
t/f about intermediate filaments, they can be anchored to the plasma membrane at a cell-cell junction
true
t/f about intermediate filaments, they can be found in the cytoplasm and the nucleus
true
t/f each calmodulin can bind to 4 calcium ions
true
t/f extracellular signal molecules that are hydrophilic must bind to a cell surface receptor so as to signal a target cell
true
t/f most g-protein coupled receptors are multipass transmembrane proteins with 7-alpha helixes
true
t/f receptor tyrosine kinases (RTK) always form dimers after binding with signal molecules
true
To study the function of keratin, which of the following models can be chosen?
zebrafish and mouse
gene regulation by mechanicotransduction
~mechanical stress > cytoskeleton >lamin >chromatin >transcription OR ~mechanical stress> cytoskeleton > chemical signals > chromatin > transcription (>transcription)
step 3 ( interphase nucleus)
continued fusion of nuclear envelope vesicles
ca2+ activates
contraction
filamin
cross-links actin filaments into network
3 types of cytoplasmic intermediate filaments
1. Keratin 2. Vimentin 3. Neurofillaments
In an experiment, you treated cells with a drug that blocks ATP synthesis, which of the following processes will be arrested immediately? Microtubule assembly, exocytosis, actin filament assembly, or cell migration
exocytosis, actin filament assembly, cell migration
To design a drug that can inhibit cancer cell migration, which protein may not be chosen as the target?
Kinesin
Taxol
binds and stabilizes microtubules
Colchicine, colcemid
binds tubulin dimers, and prevents their polymerization
Tropomyosin
blocks binding of myosin head to actin filament
GTP-tubulin leads to assembly
1. gtp tubulin diners add to growing end of mt 2. addition proceeds faster than gtp hydrolysis by the dimers
GDP-tubulin leads to disassembly
1. protofilaments containing gdp tubulin peel away from the mt wall 2. gdp tubulin is released to the cytosol
how many steps to nuclear envelope break down and reassembly
3
ACh signaling pathway
ACh > GPCR > BV (beta gamma) subunit of g protein > PLC > IP3 > Ca2 Release > calmodulin
AP pathway for contraction in skeletal muscle
AP reach t-tub. > open vol. gated Ca2+ chan > open Ca2+ release channels on SR > Ca2+ flooding > influx of Ca2+ in cytosol ? muscle contraction
Researchers studying vesicular transport assembled several transport components in vitro (in a test tube). They set up the stabilized microtubules, then added vesicles and kinesin. When they put everything together, there was no movement of transport vesicles along microtubule. What were they missing?
ATP
signaling complex
bridging signaling proteins at a specific location, allowing them to be activated at higher speed, efficiency and specifity
acetylcholine controls the contraction of skeleton muscle and smooth muscle using different signaling pathways. Which mechanism is shared by these two pathways?
Ca2+ release from SR
smooth muscle contraction, ACh binds to
GPCR, ACh receptor
Insulin signaling pathway
IRS to PI3K activates PIP2 to PIP3 to PDK1 to AKT > glut 4 release
which of the following mutations would lead to an excess in the amount of glucose in skeletal muscle cells?
a PKA mutant form in which the inhibitory subunits lose the binding ability to the kinase subunits
which of the following compounds can be potential anti-cancer drug?
a compound that activates Ras-GAP
cause of release calcium into cytosol
activate PLC-IP3 signaling pathway
adrenaline signaling pathway
adrenaline > GPCR > G protein > cAMP > PKA > PhK > metabolism
Hemidesmosomes
anchors intermediate filaments in a cell to the basal lamina
defective keratin
causes high vulnerability of the skin against mechanical injury
high dynamic structure
cell division and movement
filamentous architecture
cell shaping and organization
phalloidin
binds and stabilizes filaments
which of the following is not one of the pathways activated by RTKs?
cAMP-PKA
cause of MLCK activation
calcium binds and activates calmodulin
colchicine treatment
causes dramatic collapsing of ER around nucleus and fragment of golgi
step 2 (telophase)
dephosphorylation of these proteins > re-assembly
in MT, atp hydrolysis provides energy to
drive conformational change
To study the function of lamin, which of the following models can be chosen?
drosophila, zebrafish and mouse (can be yeast too under certain circumstances)