Cell Signaling Review Questions

1. Cell Signaling Review Questions

2. Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because: • they are species specific. • they always lead to the same cellular response. • they amplify the original signal manyfold. • they counter the harmful effects of dephosphorylaters (phosphatases). • the number of molecules used is small & fixed.

3. 2. Binding of a singling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane? • Receptor tyrosine kinase • G protein-coupled receptor • Phosphorylated receptor typrosinekinase • Ligand gated ion channel • Intracellular receptor

4. 3. The activation of receptor tyrosine kinases is characerized by: • dimerization & phosphorylation. • ATP binding. • a phosphorylation cascade. • GTP hydrolysis. • channel protein shape change.

5. 4. Protein phosphorylation is commonly involved with all of the following except: • regulation of transcription by extracellular signaling molecules. • enzyme activation. • activation of G-coupled protein receptors. • activation of receptor tyrosine kinases. • activation of protein kinase molecules.

6. 5. Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because: • only target cells retain appropriate DNA segments. • intracellular receptors are only present in target cells. • most cells lack the Y chromosome required. • only target cells posses the cytosolic enzymes that transduce testosterone. • only in target cells is testosterone able to initiate the phosphorylation cascade leading to activated transcription factor.

7. 6. Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylylcyclase → cAMP. Identify the second messenger. • cAMP • G protein • GTP • adenylylcyclase • G protein-coupled receptor