Question 1

What are the first three steps in signaling from cytokine receptors?

Accepted Answer

The answer of What are the first three steps in...

Question 2

How would a mutation in the TGF-$\beta$ type I receptor that prevented it from being phosphorylated affect the cell?

Accepted Answer

The answer of How would a mutation in the TGF-$\beta$...

Question 3

What is the role of$\beta$-arrestin in mediating crosstalk signaling between G protein-coupled receptors (GPCR) and ERK signaling?

Accepted Answer

The answer of What is the role of$\beta$-arrestin in mediating...

Question 4

Which of the following is an example of endocrine signaling?

Accepted Answer

Insulin release by F1F1F1S1βF1F1F10 cells in the pancreas is an example of endocrine signaling because it involves the release of a hormone (insulin) into the bloodstream, which then travels to target cells (muscle cells) and mediates an effect (glucose uptake). A is an example of synaptic signaling, B is an example of autocrine signaling.

Question 5

The term "paracrine signaling" refers to

Accepted Answer

Paracrine signaling refers to signaling between cells that are located close to each other. This type of signaling allows for local communication and coordination between cells. Examples of paracrine signaling include neurotransmitter release at synapses and cytokine signaling between immune cells.

Question 6

Which steroid hormone(s) is(are) not secreted by the gonads?

Accepted Answer

Corticosteroids are not secreted by the gonads. They are secreted by the adrenal cortex. Progesterone, estrogen, and testosterone are all steroid hormones that are secreted by the gonads (ovaries and testes).

Question 7

The signaling molecule nitric oxide (NO) functions

Accepted Answer

Nitric oxide (NO) is a gas that can readily diffuse across cell membranes and enter the cytoplasm. Once inside the cell, it can bind and activate intracellular enzymes, such as guanylyl cyclase, to produce the second messenger cyclic GMP (cGMP). NO typically acts in a paracrine or autocrine manner, affecting nearby cells or the same cell that synthesized it. Therefore, choices A and B are incorrect since NO does not require specific cell surface or intracellular receptors for its action. Choice C is also incorrect since NO typically acts locally, although it can diffuse over short distances.

Question 8

What is the difference between neurotransmitters and neuropeptides?

Accepted Answer

Neurotransmitters are small hydrophilic molecules that transmit signals across synapses, while neuropeptides are larger molecules made up of amino acids that act as neuromodulators rather than directly transmitting signals. The size difference between neurotransmitters and neuropeptides is related to their function and mode of action.

Question 9

Which statement regarding heterotrimeric G proteins in a resting state is true?

Accepted Answer

In a resting state, GDP is bound to the F1F1F1S1αF1F1F10 subunit in a complex with both the F1F1F1S1βF1F1F10 and F1F1F1S1γF1F1F10 subunits. This is the inactive form of the heterotrimeric G protein. When a ligand binds to the G protein-coupled receptor, it induces a conformational change that allows GDP to be exchanged for GTP on the α subunit, leading to activation of the G protein.

Question 10

G protein-coupled receptors are important molecules involved in signal transduction. Which statement about G protein-coupled receptors is true?

Accepted Answer

G protein-coupled receptors generally contain seven membrane-spanning helices, which form a structural domain called heptahelical or seven-transmembrane domain. They are activated by various ligands, including neurotransmitters, hormones, and sensory stimuli, and signal through a complex network of intracellular effector proteins mediated by G proteins. They bind guanine nucleotides only indirectly, through their interaction with G proteins. They do not specifically bind adenine nucleotides. Steroid hormones act on intracellular receptors, which are not G protein-coupled.

Question 11

Which statement about G protein signaling is false?

Accepted Answer

The statement "The F1F1F1S1F1F1F10 subunit becomes deactivated when the hormone dissociates from the receptor" is false. In reality, the activity of the F1F1F1S1F1F1F10 subunit is terminated by the hydrolysis of GTP to GDP, as stated in choice C.

Question 12

Cyclic AMP (cAMP) is synthesized from ATP by the action of

Accepted Answer

Cyclic AMP is synthesized from ATP by the action of adenylyl cyclase.

Question 13

Most of the effects of cyclic AMP (cAMP) in the cell are mediated by

Accepted Answer

The most common and well-known mediator of cAMP effects in the cell is Protein Kinase A (PKA), which is activated by binding of cAMP to its regulatory subunits, leading to the release and activation of its catalytic subunits. This activation of PKA then triggers a cascade of downstream effects, including changes in gene expression, ion channel activity, and other signaling pathways. Therefore, choice A is the best answer. Choices B and C are incorrect because cAMP is not directly involved in regulating ion channels or PKC activity. Choice D is incorrect because cAMP phosphodiesterase is actually an enzyme that breaks down cAMP, rather than mediating its effects.

Question 14

Which statement about protein kinase A (PKA) is false?

Accepted Answer

PKA binds two molecules of cAMP, one on each of the two regulatory (R) subunits. Therefore, statement B is false.

Question 15

Receptor tyrosine kinases represent critical molecules involved in growth and differentiation though phosphorylation of target substrates on tyrosine residues. Which structural feature is not common among all receptor tyrosine kinases?

Accepted Answer

Not all receptor tyrosine kinases are single polypeptides; some exist as dimers or oligomers.

Question 16

Which of the following is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor?

Accepted Answer

Binding of a signaling molecule to its cell surface receptor typically results in receptor dimerization, receptor phosphorylation, and conformational changes in the receptor. However, it does not typically result in increased synthesis of the receptor.

Question 17

SH2 domains are

Accepted Answer

SH2 domains are protein domains that specifically recognize and bind to phosphorylated tyrosine residues in proteins, particularly in signaling proteins. This binding is important for the assembly of signaling complexes and the transduction of signals downstream.

Question 18

Integrins are transmembrane proteins that connect

Accepted Answer

Integrins connect the extracellular matrix to the cytoskeleton, allowing for cell adhesion and communication.

Question 19

The MEK kinase (MAP kinase/ERK kinase) is unusual in that it

Accepted Answer

MEK kinase is unique because it is a dual-specificity kinase, meaning it can phosphorylate both threonine and tyrosine residues.

Question 20

Heterotrimeric G proteins are not the only guanine nucleotide-binding proteins. Which of the following represents a family of GTP-binding proteins that act as monomers rather than heterotrimeric compounds?

Accepted Answer

Ras proteins are monomeric GTPases, meaning they function as single units rather than forming heterotrimeric complexes. ERK (extracellular signal-regulated kinase), Raf (rapidly accelerating fibrosarcoma), and Smad (intracellular signaling molecules) are all involved in signal transduction pathways but they are not known for their GTP-binding properties.

Quiz 17: Cell Signaling

What are the first three steps in signaling from cytokine receptors?

How would a mutation in the TGF- $\beta$ type I receptor that prevented it from being phosphorylated affect the cell?

What is the role of $\beta$ -arrestin in mediating crosstalk signaling between G protein-coupled receptors (GPCR) and ERK signaling?

Which of the following is an example of endocrine signaling?

The term "paracrine signaling" refers to

Which steroid hormone(s) is(are) not secreted by the gonads?

The signaling molecule nitric oxide (NO) functions

What is the difference between neurotransmitters and neuropeptides?

Which statement regarding heterotrimeric G proteins in a resting state is true?

G protein-coupled receptors are important molecules involved in signal transduction. Which statement about G protein-coupled receptors is true?

Which statement about G protein signaling is false?

Cyclic AMP (cAMP) is synthesized from ATP by the action of

Most of the effects of cyclic AMP (cAMP) in the cell are mediated by

Which statement about protein kinase A (PKA) is false?

Receptor tyrosine kinases represent critical molecules involved in growth and differentiation though phosphorylation of target substrates on tyrosine residues. Which structural feature is not common among all receptor tyrosine kinases?

Which of the following is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor?

SH2 domains are

Integrins are transmembrane proteins that connect

The MEK kinase (MAP kinase/ERK kinase) is unusual in that it

Heterotrimeric G proteins are not the only guanine nucleotide-binding proteins. Which of the following represents a family of GTP-binding proteins that act as monomers rather than heterotrimeric compounds?

Quiz 17: Cell Signaling

What are the first three steps in signaling from cytokine receptors?

How would a mutation in the TGF- β\betaβ type I receptor that prevented it from being phosphorylated affect the cell?

What is the role of β\betaβ -arrestin in mediating crosstalk signaling between G protein-coupled receptors (GPCR) and ERK signaling?

Which of the following is an example of endocrine signaling?

The term "paracrine signaling" refers to

Which steroid hormone(s) is(are) not secreted by the gonads?

The signaling molecule nitric oxide (NO) functions

What is the difference between neurotransmitters and neuropeptides?

Which statement regarding heterotrimeric G proteins in a resting state is true?

G protein-coupled receptors are important molecules involved in signal transduction. Which statement about G protein-coupled receptors is true?

Which statement about G protein signaling is false?

Cyclic AMP (cAMP) is synthesized from ATP by the action of

Most of the effects of cyclic AMP (cAMP) in the cell are mediated by

Which statement about protein kinase A (PKA) is false?

Receptor tyrosine kinases represent critical molecules involved in growth and differentiation though phosphorylation of target substrates on tyrosine residues. Which structural feature is not common among all receptor tyrosine kinases?

Which of the following is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor?

SH2 domains are

Integrins are transmembrane proteins that connect

The MEK kinase (MAP kinase/ERK kinase) is unusual in that it

Heterotrimeric G proteins are not the only guanine nucleotide-binding proteins. Which of the following represents a family of GTP-binding proteins that act as monomers rather than heterotrimeric compounds?

How would a mutation in the TGF- $\beta$ type I receptor that prevented it from being phosphorylated affect the cell?

What is the role of $\beta$ -arrestin in mediating crosstalk signaling between G protein-coupled receptors (GPCR) and ERK signaling?