G protein coupled receptor pathway of cell signalling

The alpha subunit of a G protein is often activated by receptor tyrosine kinase.   True   False

Which of the following statements is (are) trueabout the G-protein coupled receptors (GPCRs)?A.There are only a few GPCRs in the human genome.B.When a signal molecule binds to the GPCR it causesphosphorylation of the GPCR that allows the G-proteinto bind.C.GPCRs act as GEFs for specific G-proteins.D.They are peripheral proteins composed of multiplepolypeptides.

The second messenger of the G-protein-coupled (metabotropic) receptor is:a.Phospholipase Cb.Sodium ionsc.c-AMPd.Adenylyl cyclase

The following excerpt and image come from a scientific paper written by Ebrahimi & Chess. They discuss the role of G proteins in olfaction, or the sense of smell.Each mammalian olfactory neuron appears to use the same machinery for transducing signals from its odorant receptor molecules. Upon odorant binding, the receptor is thought to activate G , a G protein. G -mediated activation of adenylate cyclase III then raises intracellular cAMP levels, causing a cyclic-nucleotide-gated channel to open. The influx of cations through this channel ultimately leads to the formation of an action potential, which allows the primary neuron to signal to the brain.A sketch of an olfactory neuron with the cilia, cell body and axon labeled. From the axon there is an arrow pointing towards the caption projects to olfactory bulb. The end of one cilia is circled and next to it there is a magnified diagram showing a cellular process. Along the membrane there is a inverted shaped molecule labeled odorant receptor, and next to the odorant receptor on the inside of the membrane is a box labeled Golf and next to the Golf box is a box with the symbols alpha and beta in the box. Beside these three boxes there is an oval that extends across the membrane labeled adenylate cyclase III. On the outside of the membrane is a triangle labeled odorant with an arrow pointing to the odorant receptor. Inside the membrane there are 2 curved arrows next to the Golf box. One arrows shows GTP pointing to GDP, and the other arrow points from Golf towards the adenylate cyclase III. Below the adenylate cyclase III there is a curved arrow showing ATP going to cAMP and then c AMP points to a channel in the membrane labeled cyclic-nucleotide-gated channel. On the outside of the membrane there is a red box with a red arrow pointing at the cyclic nucleotide gated channel and the caption inside the red box is Mutation prevents opening. There is an arrow pointing from outside the membrane towards the channel and sodium and calcium ions are inside the channel. Inside the membrane there are three arrows pointing from the channel. One arrow points to a sodium ion, one arrow points to a calcium ion, and the third arrow points to a sodium ion.Ebrahimi, F. A. & Chess, A. (1998). Olfactory G proteins: Simple and complex signal transduction. Current Biology, 8(12), R431–R433. doi:10.1016/s0960-9822(98)70271-4A mutation in a component of this signal transduction pathway prevents the cyclic-nucleotide-gated channel from opening.Which of the following scientific questions would best help researchers understand how the mutation prevents the cyclic-nucleotide-gated channel from opening?Choose 1 answer:Choose 1 answer:(Choice A)   Does the mutation stimulate the conversion of ATP to cAMP?ADoes the mutation stimulate the conversion of ATP to cAMP?(Choice B)   Does the mutation block the activation of adenylate cyclase III?BDoes the mutation block the activation of adenylate cyclase III?(Choice C)   Does the mutation promote the influx of cations into the cell?CDoes the mutation promote the influx of cations into the cell?(Choice D, Checked)   Does the mutation cause intracellular cAMP levels to rise?DDoes the mutation cause intracellular cAMP levels to rise?

When a ligand binds to a GPCR, what happens to the G-protein associated with the receptor?Question 11Answera.The β subunit activates adneylyl cyclase.b.The G-protein dissociates into its α and βγ subunits.c.The G-protein binds ATP.d.The G-protein is internalised by the cell.