Question 1

Which of the following best describes the three stages of cell signaling as shown in the first image?

Accepted Answer

Signal reception, signal transduction, and cellular response

Question 2

In the context of G protein-coupled receptor (GPCR) signaling, what is the immediate effect of GTP binding to the G protein?

Accepted Answer

The G protein becomes activated and can then activate an enzyme such as adenylyl cyclase

Question 3

Which of the following signaling molecules is most likely to bind to an intracellular receptor?

Accepted Answer

A steroid hormone such as estradiol

Question 4

What is the main function of a second messenger such as cAMP in cell signaling?

Accepted Answer

To amplify the signal inside the cell and activate downstream proteins

Question 5

Which enzyme is responsible for converting ATP to cAMP during GPCR signaling?

Accepted Answer

Adenylyl cyclase

Question 6

What is the role of protein phosphatases in a phosphorylation cascade?

Accepted Answer

They remove phosphate groups from proteins, generally inactivating them

Question 7

Which of the following best describes the process of signal amplification in cell signaling?

Accepted Answer

A single signaling molecule can trigger the production of many second messengers, each of which can activate multiple target proteins

Question 8

Which of the following is a key difference between paracrine and endocrine signaling?

Accepted Answer

Paracrine signaling acts on nearby cells, while endocrine signaling acts on distant cells via the bloodstream

Question 9

A mutation prevents the dimerization of receptor tyrosine kinases (RTKs) after ligand binding. What is the most likely consequence?

Accepted Answer

The receptors will not autophosphorylate and downstream signaling will not occur

Question 10

Which of the following best explains why steroid hormones can bind to intracellular receptors?

Accepted Answer

Steroid hormones are hydrophobic and can diffuse through the plasma membrane

Question 11

During GPCR signaling, what would be the effect of a nonfunctional phosphodiesterase enzyme?

Accepted Answer

cAMP levels would remain elevated, prolonging the cellular response

Question 12

Which of the following is a correct sequence of events for the activation of a receptor tyrosine kinase (RTK)?

Accepted Answer

Ligand binding → dimerization → autophosphorylation → activation of relay proteins

Question 13

A cell is exposed to a signaling molecule that cannot cross the plasma membrane. Which type of receptor is most likely to mediate the response?

Accepted Answer

A cell surface receptor such as a GPCR or RTK

Question 14

Which of the following best describes the function of cAMP in the GPCR pathway shown in the images?

Accepted Answer

It acts as a second messenger to activate protein kinase A

Question 15

In the context of cell signaling, what is the primary role of relay molecules?

Accepted Answer

To transmit and amplify the signal from the receptor to the target proteins inside the cell

Question 16

Which of the following equations correctly represents the conversion of ATP to cAMP by adenylyl cyclase?

Accepted Answer

$$\mathrm{ATP} \xrightarrow{	ext{adenylyl\ cyclase}} \mathrm{cAMP} + \mathrm{PP_i}$$

Question 17

A researcher adds a drug that blocks the dimerization of RTKs. Which step in the signaling pathway will be directly affected?

Accepted Answer

Autophosphorylation of the tyrosine residues

Question 18

Which of the following is a likely outcome if a mutation causes a GPCR to remain constantly active, even in the absence of a ligand?

Accepted Answer

Continuous activation of downstream signaling pathways, potentially leading to disease

Question 19

Which of the following best explains why cAMP is considered a 'second messenger'?

Accepted Answer

It relays the signal from the cell surface receptor to intracellular targets after being produced in response to the first messenger

Cell Communication and Signal Transduction

Study Guide - Practice Questions