Question 1

Which of the following best describes the difference between endocrine and paracrine signaling?

Accepted Answer

Endocrine signaling involves hormones traveling through the bloodstream to distant target cells, while paracrine signaling involves local regulators affecting nearby cells.

Question 2

Which of the following is NOT a stage in the cell signaling process as described by Earl Sutherland?

Accepted Answer

Amplification

Question 3

A hormone binds to a receptor tyrosine kinase (RTK) on the cell surface. What is the immediate result of this binding?

Accepted Answer

The RTKs dimerize and phosphorylate each other's tyrosine residues.

Question 4

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

Accepted Answer

$$\mathrm{ATP} \rightarrow \mathrm{cAMP} + \mathrm{PP_i}$$

Question 5

Which of the following best explains why the binding of a single molecule of epinephrine can result in the release of millions of glucose molecules from glycogen?

Accepted Answer

Signal amplification occurs through a phosphorylation cascade, where each step activates many molecules in the next step.

Question 6

Which of the following is a correct description of a G protein-coupled receptor (GPCR) signaling pathway?

Accepted Answer

A ligand binds to the GPCR, activating a G protein by exchanging GDP for GTP, which then activates an enzyme to produce a second messenger.

Question 7

Which of the following statements about second messengers is TRUE?

Accepted Answer

Second messengers are small, non-protein, water-soluble molecules or ions that rapidly spread signals within the cell.

Question 8

A mutation causes a cell’s receptor to remain active even when the ligand is not present. What is a likely consequence?

Accepted Answer

Uncontrolled cell division, potentially leading to cancer.

Question 9

Which of the following best describes the role of protein phosphatases in cell signaling?

Accepted Answer

They remove phosphate groups from proteins, turning off the signal transduction pathway.

Question 10

Which of the following is an example of a cellular response to a signal transduction pathway?

Accepted Answer

All of the above

Question 11

Which of the following best explains how caffeine keeps you awake?

Accepted Answer

Caffeine acts as a competitive inhibitor of adenosine receptors, preventing adenosine from causing drowsiness.

Question 12

Which of the following is a correct sequence of events for a ligand-gated ion channel?

Accepted Answer

Ligand binds to receptor, channel opens, specific ions flow through, cellular response occurs.

Question 13

Which of the following is a real-world example of a drug that acts by affecting a second messenger pathway?

Accepted Answer

Viagra, which inhibits the breakdown of cGMP, prolonging smooth muscle relaxation.

Question 14

Which of the following equations represents the phosphorylation of a protein by a kinase?

Accepted Answer

$$\mathrm{Protein} + \mathrm{ATP} \rightarrow \mathrm{Protein{-}P} + \mathrm{ADP}$$

Question 15

Which of the following is a function of apoptosis in multicellular organisms?

Accepted Answer

All of the above

Question 16

A cell receives a signal that triggers a phosphorylation cascade. What is the main advantage of this cascade?

Accepted Answer

It amplifies the signal, allowing a small number of signaling molecules to produce a large cellular response.

Question 17

Which of the following best describes the role of scaffolding proteins in signal transduction?

Accepted Answer

They increase the efficiency of signal transduction by holding multiple relay proteins close together.

Question 18

Which of the following is a possible outcome if a cell fails to terminate a signal transduction pathway?

Accepted Answer

Uncontrolled cellular responses, such as excessive growth or division.

Question 19

Which of the following best describes how a lipid-soluble hormone (such as steroid hormone) typically acts on a target cell?

Accepted Answer

It passes through the plasma membrane, binds to an intracellular receptor, and the complex acts as a transcription factor in the nucleus.

Cell Communication: Mechanisms and Pathways

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