Based on Figure 1, which of the following is the first step in the activation of cAMP-dPK?
Question:
Based on Figure 1, which of the following is the first step in the activation of cAMP-dPK?
(A) The exchange of GTP for GDP
(B) The binding of epinephrine
(C) The separation of a-GTP
(D) Phosphorylation of intracellular enzymes
G-protein coupled receptors (GPCRs) are a common type of protein receptor containing seven transmembrane segments and bearing intracellular and extracellular portions. The structure of a typical GPCR and its associated partners is shown below. GPCRs are coupled to G-proteins consisting of three subunits (a, β, and γ) that bind the nucleotides GTP or GDP on the intracellular side of the GPCR. The presence or absence of a ligand on the extracellular side of the GPCR determines whether GDP or GTP will bind to the intracellular G-protein. Extracellular ligand binding initiates GDP being exchanged for GTP and the separation of the G-protein. One subunit will travel to join with a secondary partner and will initiate a cascade of signaling effects within the cell. In the example shown below, the secondary partner is adenylyl cyclase and the signaling is cAMP upregulation.
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The Princeton Review AP Biology Premium Prep 2023
ISBN: 9780593450659
2023 Edition
Authors: The Princeton Review