Cell Biology Lectures 19-20 (Part 1)

1.

1 point

Cholera and whooping cough both are caused by bacteria that:

alter the function of G proteins.

disable a G protein.

alter the function of ion-gated channels.

take up residence inside white blood cells.

2.

1 point

Which of the following is not a small intracellular signaling molecule (second messenger)?

Cyclic AMP

Inositol triphosphate

Phospholipase C

Diacylglycerol

3.

1 point

Many of the extracellular signal molecules that regulate inflammation are released locally at the site of infection. What form of cell-to-cell signaling is being used?

Neuronal

Endocrine

Paracrine

Contact-dependent

4.

1 point

Which of the following statements is true?

Enzyme-coupled receptors always have an intrinsic catalytic domain on the cytosolic side of the plasma membrane.

Ion-channel–coupled receptors can rapidly alter the membrane potential in response to neurotransmitter binding.

G-protein–coupled receptors are GTP-binding proteins.

5.

1 point

How does IP3 function in the inositol phospholipid pathway?

It binds to and opens Ca2+ channels that are embedded in the ER membrane, releasing Ca2+ into the cytosol.

It directly activates protein kinase C.

It punches holes into the membrane surrounding the endoplasmic reticulum (ER), releasing Ca2+ from the ER into the cytosol.

It activates phospholipase C.

6.

1 point

When activated phospholipase C chops the head off an inositol phospholipid, it produces two small signaling molecules that relay the signal onward. Which of these stays in the plasma membrane?

Inositol 1,4,5-trisphosphate (IP3)

Diacylglycerol (DAG)

7.

1 point

The proteins targeted by either the /alpha subunit or the /alpha//beta complex of a G-protein are either enzymes or ion channels in the plasma membrane.

True

False

8.

1 point

GPCRs are often referred to as seven-pass transmembrane receptors because they have:

seven receptors on each side of the lipid bilayer that receive and transmit signals.

seven different G proteins with which they interact to amplify signals.

a polypeptide chain that crosses the lipid bilayer seven times.

seven pores that signal molecules can use to pass through the bilayer.

9.

1 point

The cyclic AMP pathway can both activate enzymes and turn on genes.

True

False

10.

1 point

Which component or components of a G protein can, on its own, activate downstream proteins in an intracellular signaling pathway?

(A) /alpha subunit

(B) /beta subunit

(C) /beta/gamma complex

All of the above

A and C

11.

1 point

Signaling cascades always operate at the same speeds irrespective of external stimuli.

True

False

12.

1 point

Which molecule (or molecules) performs the primary signal transduction step in a signal transduction cascade?

The extracellular signal

The intracellular protein kinases

The receptor protein

13.

1 point

Both GPCRs and RTKs can activate the inositol phospholipid signaling pathway because they both can activate phospholipase C enzymes (although the enzymes are not exactly the same).

True

False

14.

1 point

Some dissolved gases cross the plasma membrane and activate intracellular enzymes directly.

True

False

15.

1 point

Ion-channel coupled receptors:

integrate multiple signals at the same time.

are voltage-gated.

transduce signals in a simple and direct manner.

transduce signals via elaborate intracellular signaling pathways.

16.

1 point

Ca2+ is an important intracellular messenger in which types of organisms?

Animals

Plants

All eukaryotic organisms

17.

1 point

Which type of receptors do steroid hormones employ?

Nuclear receptors

Ion-channel–coupled receptors

Cell-surface receptors

18.

1 point

Which of the following pathways is activated by most RTKs?

The phosopholipase C/inositol phospholipid signaling pathway

The Ras signaling pathway

MAP-kinase signaling module

All of the above

None of the above

19.

1 point

Ras is activated by a Ras-activating protein that:

causes Ras to bind to a G protein.

dephosphorylates Ras.

phosphorylates Ras.

causes Ras to exchange GDP for GTP.

20.

1 point

The concentration of free Ca2+ in the cytosol of an unstimulated cell is kept low compared with its concentration in both the extracellular fluid and the endoplasmic reticulum. Which of the following does not help maintain this difference?

Ca2+-destroying enzymes in the cytosol

Membrane-bound Ca2+ pumps in the ER membrane

Ca2+-binding proteins in the cytosol

Membrane-bound Ca2+ pumps in the plasma membrane

21.

1 point

Many drugs act by binding to:

cell surface receptors.

protein kinases.

cyclic AMP.

nuclear receptors

22.

1 point

Following the binding of an extracellular signal molecule, receptor tyrosine kinases (RTKs) are activated by dimerization, which allows:

each polypeptide chain to cross-phosphorylate the other chain in the dimer on specific tyrosines in its cytoplasmic tail.

each polypeptide chain in the dimer to phosphorylate itself on specific tyrosines in its cytoplasmic tail.

the receptor to be internalized so that it can phosphorylate and activate various intracellular signaling proteins.

23.

1 point

The enzyme cyclic AMP phosphodiesterase helps terminate a response mediated by an increase in cyclic AMP by:

converting ATP to cyclic AMP.

converting AMP to cyclic AMP.

converting cyclic AMP to AMP.

converting cyclic AMP to ATP.

24.

1 point

The phosphorylated tyrosines on activated RTKs:

(A) help activate the kinase activity of the receptor.

(B) serve as binding sites for G proteins.

(C) serve as binding sites for a variety of intracellular signaling proteins.

All of the above

A and C

25.

1 point

Each type of extracellular signal molecule induces a similar response in different target cells.

True

False

26.

1 point

Nitric oxide (NO) acts only on neighboring cells (as a local mediator in paracrine signaling) because:

it is rapidly washed away by the blood stream.

so little is produced by the signaling cell.

it is rapidly converted to nitrates and nitrites in the target cell.

it is rapidly converted to nitrates and nitrites in the extracellular fluid

27.

1 point

What does a target cell require to respond to an extracellular signal molecule?

Access to the signal molecule

The presence of an appropriate receptor for the signal molecule

Appropriate intracellular signaling pathways

All of the above

28.

1 point

In the Notch signaling pathway, the tail of the cell surface receptor travels to the nucleus where it regulates the transcription of specific genes.

True

False

29.

1 point

Nitric oxide (NO) causes blood vessels to dilate because:

it causes endothelial cells lining blood vessels to relax.

it causes smooth muscle cells in the walls of blood vessels to relax.

it inhibits cyclic GMP production by inhibiting guanylyl cyclase.

All of the above.

30.

1 point

Which of the following statements is false?

Tyrosine protein kinases phosphorylate intracellular proteins on tyrosines.

Serine/threonine protein kinases phosphorylate extracellular proteins on serines and/or threonines.

Serine/threonine protein kinases phosphorylate intracellular proteins on serines and/or threonines.

31.

1 point

Another name for small messenger molecules is:

first messengers.

extracellular signals.

second messengers.

intracellular signaling proteins.

32.

1 point

Which G protein component or components have GTPase activity?

/beta subunit

/alpha subunit

/gamma subunit

/alpha//beta complex

33.

1 point

Most extracellular signal molecules act on cell-surface rather than intracellular receptors because they are:

either too large, too hydrophilic, or both to pass directly across the plasma membrane.

too hydrophilicto pass directly across the plasma membrane.

too large to pass directly across the plasma membrane.

34.

1 point

Mutant Ras proteins, which are found in many cancer cells, can’t hydrolyze their bound GTP to GDP, and therefore:

can‘t be degraded.

they are able to activate MAP kinase directly.

can‘t turn themselves on.

can‘t turn themselves off.

35.

1 point

A target cell can respond quickly to an extracellular signal if:

the cell does not require a receptor for the signal molecule.

the response does not require target cell proteins to be altered.

the response does not require new gene transcription or new protein synthesis.

36.

1 point

Which of the following signaling molecules don’t seem to be used by plants in cell-to-cell communication?

Ca2+

Cyclic AMP

Enzyme-coupled receptors

GPCRs

37.

1 point

Parallel intracellular signaling pathways can interact, in part, because the protein kinases in one pathway can phosphorylate and thereby regulate proteins in other pathways.

True

False

38.

1 point

RTKs can activate the enzyme phosphoinositide 3-kinase, which phosphorylates inositol phospholipids. These phospholipids then:

serve as docking sites that recruit specific intracellular signaling proteins to the plasma membrane.

serve as phosphate donors in phosphorylation reactions.

activate Ras.

activate G proteins.

39.

1 point

When activated by a GPCR, adenylyl cyclase:

converts AMP to cAMP.

converts ADP to cAMP.

converts ATP to cAMP.

converts cyclic AMP to AMP.

40.

1 point

A given steroid hormone usually regulates the same sets of genes in different types of target cells.

True

False

41.

1 point

Intracellular signaling molecules can act on either intracellular receptors or cell-surface receptors.

True

False

42.

1 point

GTP binding proteins, which act as molecular switches inside cells,:

are active when GDP is bound.

are active when GTP is bound.

turn themselves on by cleaving GTP to form GDP.

are active only in their trimeric forms.

43.

1 point

Signaling via a GPCR ceases when the /alpha subunit of an activated G protein hydrolyzes its bound GTP to GDP.

True

False

44.

1 point

Which subunit of a G protein is not tethered to the plasma membrane by a short lipid tail?

/gamma subunit

/beta subunit

/alpha subunit

45.

1 point

When cells respond to an extracellular signal, they most often convert the information from one form to another. This process is called:

signal transformation.

signal interference.

signal amplification.

signal transduction.

46.

1 point

When activated by the binding of Ca2+, calmodulin relays the Ca2+ signal onward by undergoing a conformational change and then:

binding to Ca2+-calmodulin-dependent protein kinases (CaM-kinases), which then phosphorylate other intracellular proteins.

binding to various extracellular proteins and directly activating them.

transferring its bound Ca2+ to various intracellular proteins, thereby activating them.

binding to cyclic AMP.

47.

1 point

How does Diacylglycerol (DAG) function in the inositol phospholipid pathway?

It binds to and opens Ca2+ channels in the plasma membrane, allowing extracellular Ca2+ to enter the cytosol.

It activates phospholipase C.

Together with Ca2+, it recruits PKC from the cytosol to the plasma membrane and activates it.

On its own, it recruits and activates protein kinase C (PKC).

48.

1 point

When the hormone insulin is released into the bloodstream, what form of cell-to-cell signaling is being used?

Paracrine

Neuronal

Endocrine

Contact-dependent