C2.1 化學訊息傳遞（細胞，HL）：練習題

When a signalling molecule (ligand) binds to its specific receptor on the surface of a target cell, what is the most immediate event that typically occurs?

Which of the following is an example of a common second messenger molecule that relays and amplifies signals within the cytoplasm after a cell surface receptor has been activated?

Vibrio cholerae produces a toxin that modifies the G-alpha subunit of a G-protein coupled receptor (GPCR) in intestinal epithelial cells. This modification prevents the G-alpha subunit from hydrolyzing its bound GTP into GDP. Based on the mechanism of chemical signalling, what would be the immediate cellular consequence of this toxin?

Epinephrine (adrenaline) is a water-soluble hormone that triggers the "fight-or-flight" response. In liver cells, it binds to a G-protein coupled receptor (GPCR), leading to the activation of adenylyl cyclase. Which of the following best describes the role of cAMP in this specific signalling pathway?

A mutation is identified in a G-protein coupled receptor (GPCR) signaling pathway that prevents the G-alpha subunit from dissociating from its effector protein (e.g., adenylyl cyclase) after GTP hydrolysis. If this pathway normally leads to increased cAMP levels, what would be the most likely consequence of this mutation?

For chemical signalling, explain where receptors for hydrophobic ligands, such as steroid hormones, are typically located within a target cell.

Describe how a kinase cascade contributes to both the amplification and specificity of a signal transduction pathway within a cell.

Propose a mechanism by which a cell could rapidly terminate a signal initiated by a G-protein coupled receptor, even in the continued presence of the ligand.

In the context of chemical signalling, outline two distinct mechanisms employed by cells to terminate or reduce their response to a signalling molecule. For each mechanism, briefly explain how it contributes to switching off the cellular response.

Outline the general mechanism by which a G-protein coupled receptor (GPCR) mediates a cellular response after binding to its specific ligand. Include the roles of the G-protein and a secondary messenger in your explanation.