Cell Biology Lectures 19-20 (Part 3)

1.

1 point

Which of the is not one of the signaling through GPCRs is highly regulated

Regulation at initiation step

Regulation at stop step

Regulation at attenuation step

None of the Above

2.

1 point

What do trimeric G proteins typically signal to for message relay?

G proteins can signal to ion channels

G proteins can activate the enzyme adenylyl cyclase (makes cAMP)

G proteins can activate the enzyme phospholipase C (makes inositol triphosphate and DAG)

All of the Above

3.

1 point

The heartbeat is controlled by G protein regulation of an ion channel.

True

False

4.

1 point

Ras is a _______ G protein.

Monomeric

Dimeric

Trimeric

None of the above

5.

1 point

G protein activation of adenylyl cyclase. Which one is false?

When we are frightened, adrenal glands release adrenaline and adrenaline

PKA activates phosphorylase kinase, then activates glycogen phosphorylase, and breaks down glycogen, and maximizes glucose available for muscular activity

Adenylyl cyclase converts ATP into cAMP and cAMP activates the kinase PKA

It has a slow response.

6.

1 point

Why have cells evolved intracellular Ca2+ stores when there is abundant extracellular Ca2+ ? (Which one is false)

ER membranes are extensive when compared to the plasma membrane surface

Ca2+ stored in ER can therefore be quickly distributed throughout cell prior to degradation.

Activated calmodulin binds to target proteins and activates them

None of the above

7.

1 point

Which of the following is false about the αlpha subunit of the G protein has an intrinsic GTPase-
allows response to be shut off

G protein is active for a long period of time

Hydrolysis of GTP by the alpha subunits inactivates this this subunit and causes it to dissociate from the target protein

Inactivate alpha subunit reassembles with beta complex to reform an inactive G protein

None of the Above

8.

1 point

After RTKs activate PI 3-K, PI 3-K converts _____ into _____.

PIP1 and PIP2

PIP2 and PIP3

PIP3 and PIP4

None of the Above

9.

1 point

Release of Ca2+ is triggered by:

GPCR signaling

Fertilization

Trigger of developmental program of an embryo

Muscle contraction

All of the above

10.

1 point

Which of the following is correct about GPCRs

Largest family of cell-surface receptors and smell and taste controlled by GPCRs

Varied ligands include: proteins, small peptides, amino acids derivatives, fatty acids, a photon of light, odorants

Over 700 in humans, including 150 orphan receptors with no known ligand and half of all known drugs work through GPCRs

All of the above

11.

1 point

RTKs dimerize upon activation.

True

False

12.

1 point

SH2 domain functions as a “plug" (Which one is not true)

Module can be inserted in proteins without disrupting structure

Specificity comes with binding site for second amino acid side chain

Cell motility effects: “fast” signaling by reconfiguration of the cytoskeleton. These signaling factors attached to surfaces over which cell is crawling

None of the above

13.

1 point

Ca2+ stores exist in the cell inside which two organelles?

ER & Mitochondria

ER & Nucleus

ER & Golgi

ER & Lysosomes

14.

1 point

What is the name of the signaling cascade that Ras activates?

MAP-kinase casacade

RTKs activate Ras

Monomeric GTPase

None of the Above

15.

1 point

Which of the following is false about activation of Akt promotes cell survival by inactivating Bad

Akt phosphorylates and inactivates Bad

In active state, Bad promotes cell death by sequestering Bcl-2, an inhibitor of apoptosis

Akt indirectly promotes cell survival

None of the Above

16.

1 point

Ras activates a MAP-kinase cascade because:

Signaling molecules can be monomers or dimers

These receptors often have implications in cancer as they are used to signal cell growth, proliferation and migration.

Mitogen has an extracellular signal that stimulates cell proliferation

All of the above

17.

1 point

PKA can activate transcription factors.

True

False

18.

1 point

The largest class of enzyme-coupled receptors are receptor tyrosine kinases (RTKs) and have which of the following functions:

Dimerization activates intrinsic tyrosine kinase activity

Receptor subunits phosphorylate each other on tyrosines

Receptorphosphorylates other proteins on tyrosines

All of the above

19.

1 point

RTK activation assembles a signaling complex because:

Activated RTK recruits signaling complex

The recruited proteins can bind to phosphorylated tyrosines through SH2 domains

Assemblies can contain 10-20 proteins

All of the above

20.

1 point

Signaling complex is

Proteins contain SH2 domains to bind phospho-Tyr

Some proteins are themselves phosphorylated on tyrosines and then activated - propagate signal

Some proteins are simply adapters

All of the above

21.

1 point

Ras is localized freely in the ________

It is tethered to ER via a lipid attachment

It is tethered to membrane via a lipid attachment

It is tethered to cytosol via a lipid attachment

It is tethered to nucleus via a lipid attachment

22.

1 point

Which one explains the relation between Ras and cancer

Akt phosphorylates and inhibits a protein that helps keep Tor shut down and activated Tor inhibits protein degradation and stimulates protein synthesis

30% of human cancers have a mutation in the Ras gene leading to aberrant activation and have mutations in the pathway

Similar to the αlpha subunit of a G protein, RTKs function through adaptor proteins to activate Ras and activated Ras has GTP bound in place of GDP

None of the Above

23.

1 point

Which of the following is not true about Cholera toxin preventing the shut-off of GPCR signalling

Cholera caused by infection of bacterium Vibrio cholerae and bacteria produces cholera toxin

Toxin enters cells lining intestine and modifies α subunit of particular G protein so it can no longer hydrolyze bound GTP

G protein cannot leave active state and results in prolonged outflow of chloride ion and water into gut

Diarrhea, dehydration, death and diarrhea helps bacteria move from host to host

None of the above

24.

1 point

Activation of phospholipase C by G proteins creates which two molecules?

IP3 and DAG

PKA and cAMP

IP3 and CaO

DAG and CaO

25.

1 point

What must bind to calmodulin before it can activate target proteins?

At least 1 Calcium (Ca2)

At least 2 Calcium (Ca2)

At least 3 Calcium (Ca2)

At least 4 Calcium (Ca2)

26.

1 point

G proteins can activate membrane-bound enzymes to make small intracellular signaling molecules (Which one is not true)

Phospholipase C (makes inositol triphosphate)

Adenylyl cyclase (makes cAMP)

Adenylyl cyclase (makes DAG)

Phospholipase C (makes DAG)

27.

1 point

Calcium binding changes the shape of the calmodulin protein, which then activates CaMK and other kinases because:

Activated calmodulin binds to target proteins and activates them

One example is Ca2+/ calmodulin-dependent CaM-Kinases (CaMKs)

CaMK in brain modulates learning and memory

All of the above

28.

1 point

Ca2+ freely diffuses in an out of cell membranes.

True

False

29.

1 point

Activated RTKs recruit other kinases and adaptor proteins.

True

False

30.

1 point

AKT is activated by binding to PIP3.

True

False

31.

1 point

Muscle contraction is regulated by Ca2+.

True

False

32.

1 point

Activation of adenylyl cyclase by G proteins creates which secondary messenger?

Small Messenger cAMP

PKA

Small Messenger cADP

Small Messenger cATP

33.

1 point

IP3 causes release of ________ from the ER

Ion-Phosphate

Calcium

Oxitoxin

Potassium

34.

1 point

Which of the following is not one of the method of activation of AKT promote cell growth and survival?

Inactivates Bad, freeing Bcl-2 so that it can inhibit apoptosis.

Inactivates Tor inhibitor, thus activating Tor and allowing it to increase synthesis, leading to cell growth

Inactivates βγ complex of the G protein binds to K+ channel

None of the above

35.

1 point

Activated Akt stimulates cell growth by indirectly activating Tor because:

Akt phosphorylates and inhibits a protein that helps keep Tor shut down and activated Tor inhibits protein degradation and stimulates protein synthesis

Ras is a monomeric GTP binding protein that bound by a lipid to the plasma membrane

Similar to the αlpha subunit of a G protein, RTKs function through adaptor proteins to activate Ras and activated Ras has GTP bound in place of GDP

None of the Above

36.

1 point

Enzyme-coupled receptor ligands has which of the following functions

Most growth factors function as local mediators

Growth effects: “slow” signaling- require transcription and translation of new proteins to give response. Diffusible signaling factors.

Cell motility effects: “fast” signaling by reconfiguration of the cytoskeleton. These signaling factors attached to surfaces over which cell is crawling

All of the above

37.

1 point

Enzyme-coupled receptors are

Signaling molecules can be monomers or dimers

These receptors often have implications in cancer as they are used to signal cell growth, proliferation and migration.

Receptor acts as an enzyme itself

All of the above

38.

1 point

What is the name of a kinase that cAMP activates?

PMA

PKA

PDA

PTA

39.

1 point

RTKs are the largest class of enzyme-coupled receptor.

True

False

40.

1 point

Upon dimerization, RTKs phosphorylate each other on ser/thr.

True

False

41.

1 point

RTKs activate PI 3-kinase leading to Akt activation

Signals such as IGF activate RTK and RTK activates PI 3-K

PI 3-K converts PIP2 to PIP3 and PIP3 recruits various signaling proteins including Akt

Akt promotes cell growth and survival by inactivating various factors such as Bad

All of the above

42.

1 point

Which of the following is true about trimeric G-proteins relay signals from GPCRs

G protein dissociates from receptor once activated, often into an activated α subunit and an activated βγ subunit, both of which may relay signals

One receptor can activate many G proteins even when the signal is not bound

Signal binds GPCR and changes receptor conformation and causes large conformational change in G protein, thus activating it

This allows association with trimeric G protein, and induces the α subunit of the G protein to release GDP and bind GTP

43.

1 point

The α subunit G proteins has an intrinsic GTPase.

True

False

44.

1 point

Most RTKs activate Ras, a monomeric GTPase (Which one is false)

Akt phosphorylates and inhibits a protein that helps keep Tor shut down and activated Tor inhibits protein degradation and stimulates protein synthesis

Ras is a monomeric GTP binding protein that bound by a lipid to the plasma membrane

Similar to the αlpha subunit of a G protein, RTKs function through adaptor proteins to activate Ras and activated Ras has GTP bound in place of GDP

None of the Above

45.

1 point

G proteins can directly regulate ion channels

Nerves that slow heart release acetylcholine and binds GPCR on heart muscle cells

Activated βγ complex of the G protein binds to K+ channel and K+ flows out of the cell

Cell’s electrical excitability is decreased

All of the Above

46.

1 point

G proteins are typically active for a long time.

True

False