Question 1

Which of the following signaling pathways is in the correct order?

Accepted Answer

The correct order for a typical signaling pathway involving these components is: Receptor → Grb2 → Sos → Ras. Grb2 is an adaptor protein that binds to activated receptors, Sos is a guanine nucleotide exchange factor (GEF) that activates Ras by facilitating the exchange of GDP for GTP on Ras.

Question 2

Which of the following statements about AKT is FALSE?

Accepted Answer

All of the statements about AKT are true, therefore none of the statements are false.

Question 3

Which of the following molecules is NOT a downstream effector of Ras?

Accepted Answer

Grb2 is an upstream effector of Ras and is not a downstream effector. Ral-GEFs, PI3K, and Raf are all downstream effectors of Ras.

Question 4

Following serum starvation,if normal fibroblasts were treated with cycloheximide to shut down cellular protein synthesis,then,when exposed to fresh serum,the cells would

Accepted Answer

During serum starvation, normal fibroblasts enter quiescence and cellular protein synthesis shuts down. When exposed to fresh serum, the cells will express immediate early genes, which are genes that are rapidly induced by serum stimulation and are required for cell cycle entry and progression. This response is independent of protein synthesis, as cycloheximide shuts down protein synthesis but does not affect the induction of immediate early genes. Therefore, the cells will express immediate early genes even in the presence of cycloheximide.

Question 5

Which of the following does NOT occur downstream of epidermal growth factor binding to its receptor?

Accepted Answer

Downstream of epidermal growth factor binding to its receptor, NF1 is phosphorylated, Ras is GTP-loaded, and the MAPK pathway is activated. However, NF1 levels are not increased as a result of this signaling pathway.

Question 6

What happens in cells following stimulation with growth factors?

Accepted Answer

Upon stimulation with growth factors, some genes required for growth are transcribed immediately, while others are transcribed later, after new transcription factors have been synthesized. This delayed response allows for a more controlled and coordinated response to the stimulus.

Question 7

In normal cells,Ras-GAPs trigger GTPase activity in order to

Accepted Answer

Ras-GAPs trigger GTPase activity in order to inactivate Ras signaling. This is because active Ras promotes cell proliferation and survival, and its deregulation can lead to cancer. Therefore, controlling Ras activity is important for maintaining normal cell functions.

Question 8

Which of the following pathways activated downstream of Ras can result in reorganization of the cytoskeleton,playing a role in cell motility?

Accepted Answer

Ral BP1 is involved in the reorganization of the cytoskeleton and plays a role in cell motility by interacting with the Ral GTPases, which are downstream of Ras.

Question 9

Which of the following domains of Src is its catalytic domain?

Accepted Answer

The catalytic domain of Src is the SH1 domain, which contains the tyrosine kinase activity. The SH2 and SH3 domains are involved in protein-protein interactions, and the C- and N-termini have regulatory roles.

Question 10

SH2 domains of tyrosine kinases function to

Accepted Answer

SH2 domains of tyrosine kinases function as both receptors for phosphotyrosine-containing oligopeptide ligands (B) and localization modules that direct the protein to specific sites in the cell (C).

Question 11

Which of the following is NOT true of the son of sevenless Sos)protein?

Accepted Answer

The statement "It is a GTPase-activating protein (GAP)" is not true of the son of sevenless (Sos) protein. Sos is a guanine nucleotide exchange factor (GEF) that activates Ras by promoting the exchange of GDP for GTP. GAPs, on the other hand, serve to deactivate Ras by accelerating its intrinsic GTPase activity.

Question 12

Which of the following is NOT true of β-catenin?

Accepted Answer

β-catenin does not bind directly to the Wnt protein. Instead, Wnt signaling inhibits the degradation of β-catenin, allowing it to accumulate and enter the nucleus where it can influence gene expression by associating with Tcf/Lef transcription factors.

Quiz 6: Cytoplasmic Signaling Circuitry Programs Many of the Traits of Cancer