Which of the following cellular responses to GPCR stimulation would be expected to occur most rapidly?

• A. Cell proliferation
• B. Activation of gene transcription
• C. Synthesis of new proteins
• D. Opening of an ion channel

Answer: (D)

Verified step by step guidance

1. Understand the role of G-protein-coupled receptors (GPCRs): GPCRs are membrane proteins that transmit signals from extracellular stimuli to intracellular signaling pathways. These signals can lead to various cellular responses, depending on the downstream effectors activated.
2. Analyze the options provided: The options include cell proliferation, activation of gene transcription, synthesis of new proteins, and opening of an ion channel. Each of these processes occurs at different speeds based on the complexity of the signaling pathway and the cellular machinery involved.
3. Consider the time required for each process: Processes like cell proliferation, gene transcription, and protein synthesis involve multiple steps, such as activation of transcription factors, mRNA synthesis, and translation, which are relatively slow. In contrast, the opening of an ion channel is a direct and rapid response to GPCR activation.
4. Relate GPCR signaling to ion channel activation: Some GPCRs activate ion channels through second messengers like cyclic AMP (cAMP) or by directly interacting with G-proteins. This interaction can cause the ion channel to open almost immediately, allowing ions to flow across the membrane.
5. Conclude that the opening of an ion channel is the fastest response: Since ion channel opening involves fewer intermediate steps and occurs directly at the membrane, it is the most rapid cellular response to GPCR stimulation among the options provided.