Cell Communication

1. Chapter 11 Cell Communication Questions prepared by Louise PaquinMcDaniel College

2. Receptor Relay molecules Transduction Activation of cellular response Signaling molecule Response Reception Signal OverviewIndicate where each of the labels should appear in the figure.

3. Signal TransductionWhich of the following best describes a signal transduction pathway? • binding of a signal molecule to a cell protein • catalysis mediated by an enzyme • sequence of changes in a series of molecules resulting in a response • binding of a ligand on one side of a membrane that results in a change on the other side • the cell’s detection of a chemical or mechanical stimulus

4. ReceptorsWhat are the similarities among the following? • G protein-coupled receptors • receptor tyrosine kinases • ion channel receptors

5. Steroid ReceptorsA steroid hormone binds to an intracellular receptor. When it does, the resulting complex is able to do which of the following? Why? • open channels in the membrane for other substances to enter • open channels in the nuclear envelope for cytoplasmic molecules to enter • mediate the transfer of phosphate groups to/from ATP • act as a transcription factor in the nucleus • make water-soluble molecules able to diffuse across membranes

6. CascadeWithout consulting the figure in your text, describe what is happening at each of the stages labeled 2 through 5.

7. PhosphorylationIn reactions mediated by protein kinases, what does phosphorylation of successive proteins do to drive the reaction? • make functional ATP • change a protein from its inactive to its active form • change a protein from its active to its inactive form • alter the permeability of the cell’s membranes • produce an increase in the cell’s store of inorganic phosphates

8. Signal MoleculesWhat would happen to a cell whose receptors remain bound to the signal molecule(s)?

9. Signal AmplificationWhich of the following is an example of signal amplification? • catalysis of many cAMP molecules by several simultaneously binding signal molecules • activation of 100 molecules by a single signal binding event • activation of a specific gene by a growth factor • activation of an enzyme molecule • utilization of a second messenger system

10. Cancer and ApoptosisHow could cancer result from a defect in apoptosis?

11. ApoptosisOne of the important outcomes of apoptosis is protection of neighboring cells. Which of the following is responsible? • cell shrinkage and blebbing • destruction of the cell’s DNA • formation of numerous vesicles to be digested • action of tyrosine kinases • activation of specific proteins