An extracellular signal molecule can act to change a cell\'s behavior by acting

Question

An extracellular signal molecule can act to change a cell's behavior by acting through cell surface _____ that control intracellular signaling proteins. These intracellular signaling proteins ultimately change the activity of _______ proteins that bring about cell responses. Intracellular signaling proteins can ______ the signal received to evoke a strong response from just a few extracellular signal molecules. A cell that receives more than one extracellular signal at the same time can ______ this information using intracellular signaling proteins. ______ proteins can act as molecular switches, letting a cell know that a signal has been received. Enzymes that phosphorylate proteins, termed ______, can also serve as molecular switches: the actions of these enzymes are countered by the activity of ______ G-protein-coupled receptors (GPCRs) all have a similar structure with ______ transmembrane domains. When a GPCR binds an extracellular signal, an intracellular G protein, composed of ______ subunits, becomes activated. ______ of the G-protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the alpha subunit is bound to ______, which is exchanged for ______ on stimulation. The intrinsic ______ activity of the alpha subunit is important for inactivating the G protein. ______ inhibits this activity of the alpha subunit, thereby keeping the subunit in an active state. The four phases of the cell cycle, in order, are G_1, ______, and ______. A cell contains the most DNA after ______ phase of the cell cycle. A cell is smallest in size after ______ phases of the cell cycle. Growth occurs in ______, and ______ phases of the cell cycle. A cell does not enter mitosis until it has completed ______ synthesis.

Explanation / Answer

5) GPCRs all have a similar structure with seven transmembrane domains.When an GPCR binds an intracellulae G protein composed of three sub units,becomes activated.Two of the G protein sub unit are thethered to the plasma membrane by short lipid tails.When unstimulated the alpha sub unit is bound to GTP which is exchanged for GDP on stimulation.The intrinsic GTPase activity of the alpha subunit is important for inactivating the G protein.Choleratoxin inhibits this activity of the alpha subunit,thereby keeping the subunit in active state.

6)The four phases of the cell cycle in order are G1,S,and G2 .A cell contains the most DNA after S phase of the cell cycle.A cell is smallest in size after M phase of cell cycle.Growth occurs in G1, S and G2 phases of cell cycle.A cell does not enter mitosis until it has completed DNA synthesis.

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