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Multiple Choice
Histamine causes all of the following reactions. Which occurs first after histamine binds to its receptor on a target cell?
A
Release of nitric oxide
B
Recruitment of immune cells to the site
C
Activation of a G protein
D
Increased vascular permeability
Verified step by step guidance
1
Understand the role of histamine: Histamine is a signaling molecule involved in immune responses, inflammation, and allergic reactions. It binds to specific histamine receptors on target cells to initiate a cascade of cellular events.
Identify the receptor type: Histamine typically binds to G-protein-coupled receptors (GPCRs). These receptors are integral membrane proteins that activate intracellular signaling pathways upon ligand binding.
Explain the mechanism of GPCR activation: When histamine binds to its receptor, the receptor undergoes a conformational change, which activates an associated G protein. This activation is the first step in the signaling cascade.
Clarify the downstream effects: After the G protein is activated, it can lead to various cellular responses, such as the release of nitric oxide, recruitment of immune cells, and increased vascular permeability. These are secondary events that occur after the initial activation of the G protein.
Summarize the sequence: The activation of the G protein is the first event after histamine binds to its receptor. This step is crucial for initiating the subsequent cellular responses, including nitric oxide release, immune cell recruitment, and changes in vascular permeability.