CSF Exam 3

During nervous-system development in Drosophila, the membrane bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in \_____ signaling

Contact Dependent

If signaling molecules act on the same cells that release them, it is an example of \____ signaling

autocrine

Monomeric GTPases are in "ON-State (active)" upon binding to:

GTP

Which of these occur more rapidly in response to a signal?

Changes in protein phosphorylation (as opposed to changes in mRNA synthesis)

Which of these best describe the GPCRs?

All receptors of this class are polypeptides with seven transmembrane segments ( most use ion channel coupling, coupled with trimeric G proteins)

The length of time a G protein will signal is determined by:

The GTPase activity of G alpha (phosphatases work on S,T,Y residues, not on G alpha directly)

The two monomers in a receptor tyrosine kinase dimer phosphorylate each other and the process is called:

Trans-autophosphorylation

Which of the following mechanisms is not directly involved in inactivation an activated RTK (Receptor Tyrosine Kinase)?

Dephosphorylation by serine/threonine phosphatases (key word serine/threonine, not tyrosine

Which of the following events does not usually occur during interphase?

The nuclear envelope breaks down

Progression through the cell cycle requires a cyclin to bind to a Cdk because:

the binding of a cyclin to Cdk is required for Cdk enzymatic activity

Substrate specificity is highly dependent on which of these subunits of PP2A phosphatase?

Regulatory subunit

Which statement is false?

Activation of MCDK activates PP2A-B55 (activation of MCDK inhibits PP2A-B55. MCDK stimulates Cdc25 activity and inhibits Wee1)

Which complex of APC/C is active in early G1?

APC/C-Cdh1 (C-Cdc20 is active at the onset of anaphase)

Activation of APC/C is important for:

Metaphase to Anaphase transition (not entry into prophase or G2-M transition)

Activation of which of these factors inhibit MCM2 loading onto DNA?

S-Cdk (Cdt1, Cdc6, ORC all help load)

At the end of DNA replication, the sister chromatids are held together by the:

cohesins

The concentration of M cyclin:

falls toward the end of M phase as a result of ubiquitination and degradation (each phase has a cyclin that goes up)

Consider the centrosome duplication cycle and in relation to replication, centrosome duplication:

Semi-conservative (not totally conservative, original gets reused but you're still making a new one)

For mictrotubule (spindle) organization in mitosis, chromosomes are not as important as centrosomes

False

Actin and myosin filaments are also main components of the mitotic spindle

false ( spindles are mostly Microtubules)

A malignant tumor is more dangerous than a benign tumor because:

its cells invade surrounding tissue

A single mutation is enough to convert a normal cell to a cancer cell

false

A great deal of lactate is produced in tumor cells even in the presence of oxygen

true (warburg effect)

The surrounding network of connective tissue that supports the tumor is called:

stroma

Which of these inhibits MCdk activity in anaphase?

activation of APC/Cdc20

Which of these is a CDK inhibitor, whose transcription is induced by p53?

p21

Inhibition of Rb activity by mutation in just one allele is sufficient to cause retinoblastoma

false

Some genes are important for normal growth but the can have gain-of-function mutations that make them cancer drivers. These genes before they gain such mutations are called:

proto-oncogenes

Which of the follow leads to hyperactivation of PI3K?

Loss of expression of PTEN (PTEN inactivates PI3K)

The loss of p53 protein makes some cancer cells less sensitive to irradiation and to some anti-cancer drugs, which would otherwise destroy tumors by inducing cell death or by inducing cell cycle arrest

true

Immediate results of the Ames test will identify:

mutagenic nature of chemicals (is it/how strong of a mutagen)

A GAP:

enhances the GTP hydrolysis rate of monomeric GTPases

An extracellular signal that is in the vicinity of the cell that secretes it and thereby activates signaling in the surrounding cells is classified as:

paracrine signaling

Endocytosis of receptors followed by degradation in lysosomes in response to a signal is a mode of:

receptor desensitization

Which of these domains bind to proline-rich sequences?

SH3 domain

Which of these is not a type of receptor?

monomeric G protein (GPCRs, enzyme coupled, and ligand gated ion channels are all receptors)

Which of these responses to a signal are likely to occur in seconds?

Protein phosphorylation (not translation, transcription, or altered cell growth)

Which of these statements is false?

Phosphates catalytically remove the phosphate from the GTP in GTP binding proteins (gdp is exchanged for gtp to activate gtp binding proteins, and serine/threonine specific kinases are common types of protein kinases)

\____ cells in select tissues release hormones that are distributed to the rest of the body:

Endocrine

Among which of these signaling mechanisms (other than endocrine) do signaling omlecules move farthest away from the cells that release them?

paracrine

Which of these are secreted extracellular signaling molecules that work only in the neighborhood they are released in?

Local mediators (not hormones or receptors)

Electrical impulses sent along a neuronal axon reaches the synapse and triggers secretion of a chemical called:

neurotransmitter

Charged phosphoinositides are recognized and bound by:

Pleckstrin Homology domain

Scaffold protein affect amplification and speed of signal by:

Limiting amplification but improving speed

Src homology domains (SH2) bind to which of these residues on activated receptors?

Phosphorylated tyrosine

Activation of which of these proteins leads to the activation of a monomeric GTPase by releasing GDP and binding GTP?

GEF

Which of these enzymes phosphorylate a protein by transferring the terminal phosphate from ATP onto a serine, threonine, or tyrosine residue?

Kinase

A signaling molecule can generate a strong signaling response that persists even after the signaling molecule is removed and this can be due to:

positive feedback

Amplification of response to a signal can be generated when receptor activation leads to a generation of a large number of intracellular signaling molecules called

second messengers

alpha subunit of G protein is bound to \_____, that is replaced with \_____ upon activation of GPCR

GDP, GTP

Inactivation of the alpha subunit of a trimeric G protein is enhanced by:

GAP activity of RGS (regulator of G protein signaling)

cAMP is synthesized from ATP by:

adenylyl cyclase

Response to a signal reaches a maximum level before it shuts itself off followed by another pulse of maximal response even in the presence of the signaling molecule leading to an oscillatory response due to:

negative feedback with a long delay

PKA is activated by binding of cAMP to the:

regulatory subunits (not catalytic subunits)

Which type of mutation in the regulatory subunits of PKA would lead to a permanently inactive state?

Mutation in the regulatory subunits that prevents the release of the catalytic subunits (not in permanent binding of cAMP or preventing regulatory subunits from binding to catalytic)

NO produced in endothelial cells diffuses across the membranes into smooth muscle cells to stimulate synthesis of cGMP by binding to:

Guanylyl cyclase

NOS catalyzed deamination of which of these amino acids produces NO?

Arginine

Cholera toxin activates the alpha subunit of Gs by ADP ribosylation which:

inhibits the GTP hydrolysis activity of alpha subunit

Increase in cAMP levels by extracellular signals can be balanced by breakdown of cAMP by enzyme:

cAMP phosphodiesterase

Activation of phospholipase C by G protein leads to:

cleavage of inositol phospholipids

Exposure of target cells to prolonged signals can lead to desensitization of GPCR by:

binding of arrestin to phosphorylated GPCR

IP3 produced by phospholipase C activation binds to IP3 receptors and leads to:

release of calcium from ER into cytosol

Which of these statements about nuclear receptors are true?

They can activate or repress transcription based on the type of receptor

Mutations that disrupt the tyrosine 1009 and 1021 residues in PDGF receptor:

disrupt the binding of SH2 domains in phospholipase C-gamma

PI3 Kinase:

is counteracted by PTEN phosphatase (doesn't activate PDK1 by phosphorylating serine residue, doesn't remove phosphate groups from S or T)

Which of these do not describe notch?

Notch tail is released to activate transcription (it is a cell surface receptor activated by proteolytic processing that involves cleavage steps)

Mutations that disrupt the protease activity of gamma secretase will:

inhibit transcription of notch target genes

Mutations in the SH2 domains of the Grb2 (growth factor receptor bound protein) adaptor that inhibit recognition of RTKs will lead to:

inhibition of GTP binding to Ras

Activation of the EGF receptor includes which of these mechanisms?

Conformational change in the receiver (not monomerization of receptors, phosphorylation by activator and receiver, or phosphorylation of both monomers by only activator)

In reference to AKT dependent regulation of Bad, select the statement that is false:

in the absence of a survival signal, Bad is phosphorylated (in the absence of a survival signal bad inhibits cell death inhibitor Bcl2, in the presence of a survival signal Akt is phosphorylated, with survival signal Bcl2 is active)

AKT and ERK activate mTORC1 activity by directly phosphorylating and inhibiting which of these GAPs?

TSC

Upon activation of Ras, the final kinase activated in the MAP Kinase module is...........

Erk

What of these statements about mTORC1 or mTORC2 are true?

mTORC1 is sensitive to rapamycin

The GEF that activates Rag GTPase is..............

Ragulator

Mutations that inhibit TSC activity leads to the disease- Tuberous Sclerosis that has benign tumors and giant cells and this is due..............

high mTORC1 activity

Enhancement of Gator1 GAP activity will lead to.................

inhibition of mTORC1 activity.

In the absence of a Wnt signal.............

Beta-catenin is degraded.

Degradation of Beta-Catenin by the proteasome is stimulated by..................

phosphorylation of Beta-Catenin by GSK3 and CK1.

Which of these events are likely to occur if Beta-Catenin is unable to bind to LEF1/TCF in the presence of Wnt signal?

Groucho will remain bound to LEF1/TCF.

A receptor tyrosine kinase-A (RTK-A) is activated by binding to a growth factor (GF). Which type of mutation is likely to inhibit the dimerization of RTK.

a mutation that prevents RTK-A from binding to GF

All GPCRs act by increasing cAMP?

False

What domain of son of sevenless (Sos) recruits it to the plasma membrane so that it gets in close proximity to Grb2?

PH

Mutations altering the GPCR binding interface in arrestin are likely to..................

prevent desensitization of GPCRs.

For Notch to be recognized by Delta, it has to be transported to the..............

plasma membrane

PI3 Kinase primarily phosphorylates...............

phospholipids

Which of these enzymes is bound to the cytosolic side of the plasma membrane and converts PI(4,5)P2 to IP3 and diacylglycerol?

phospholipase C beta

Why doesn't the beta subunit of the trimeric G-protein need a lipid anchor like the alpha and gamma subunits?

it effectively uses the gamma's anchor.

Select the mechanism of activation of AKT by PI-3K ?

It activates the receptor tyrosine kinase activity to directly phosphorylate AKT.

G-proteins are bound to GPCRs......................

at the intracellular side of the plasma membrane.

Mutations in Ras are found in a majority of cancers. Which of these mutations will lead to permanent activation of Ras-signaling?

Mutations that inhibit Ras-GTPase activity

Which of these kinases is activated by binding to diacylglycerol that is released by breakdown of PI(4,5)P2?

protein kinase C

Which of these factors belong to a family of local mediators that were originally identified as the gene important for wing development in Drosophila?

Wnt

Which mechanism is NOT likely to sharpen the cellular response to a signal?

Activating enzymes for the forward and back reactions sharpens the response.

DNA replication is initiated by\____________.

S-Cdk

M-Cdk complex is activated by\_______.

dephosphorylation by Cdc25 phosphatase.

CKIs such as p27 \____________.

inhibit the cyclin-Cdk complex

Cdk activity is stimulated by phosphorylation of the T-loop by \________.

CAK

EdU incorporation marks cells in..........

S phase

M-cyclin \_______________.

levels fall toward the end of M phase as a result of ubiquitylation and degradation.

Which of these techniques can be used to separate cells rapidly based on their fluorescence signal corresponding to their DNA content?

Flow cyclometry