Question

Place the following events in the correct order: 1. Replacement of GDP by GTP on the Ga subunit, 2. Ga subunit with its attached GTP activates effector, 3. Binding of a hormone or neurotransmitter to a G protein coupled receptor, 4. G protein binds to activated receptor forming a receptor G protein complex, 5. Dissociation of Ga from the G protein complex?

1) 4,3,1,2,5
2) 4,3,5,2,1
3) 2,3,1,4,5
4) 3,4,5,2,1
5) 3,4,1,5,2

Answer 1

The correct sequence of events for signaling through a G-protein-coupled receptor is binding of a ligand to the receptor, receptor-G protein complex formation, GDP-GTP exchange on the α subunit, α subunit dissociation, and activation of an effector by the α subunit.

Step-by-step explanation:

The correct order of events during cell signaling through a G-protein-coupled receptor (GPCR) is as follows:

1. Binding of a hormone or neurotransmitter to a G protein coupled receptor.
2. G protein binds to activated receptor forming a receptor-G protein complex.
3. Replacement of GDP by GTP on the α subunit.
4. Dissociation of α from the G protein complex.
5. α subunit with its attached GTP activates effector.

Once a signaling molecule, such as a hormone or neurotransmitter, binds to the GPCR, a conformational change allows the G protein to bind to the receptor. This triggers the replacement of GDP with GTP on the G protein α subunit. The α subunit then dissociates from the βγ complex and goes on to activate an effector. This sequence of events is crucial in the regulation of various physiological processes.