Question

1.Every step in a signal transduction pathway has an ‘on’ and ‘off’ switch. Describe the ‘on/off’ switch mechanisms (enzyme reactions) that controls the activity of adenylyl cyclase.

2.Explain the difference between endocrine and paracrine cell signaling.

Answer 1

1.When a ligand binds to a cell surface receptor,the receptor's intracellular domain changes in some way.Generally,it takes on a new shape ,which may make it active as an enzyme or let it bind other molecules.The change in the receptor sets off a series of signalling events.For instance ,receptor may turn on another signalling molecule inside of the cell,which in turn activates own target.This chain reaction can eventually lead to a change in the cell's behavior or characteristics.

2.Endocrine responses are slow and long because the harmone needs to be filtered out of the blood before it can take effect while paracrine describes harmone action where harmones are released from cells and bind to receptor on nearby cells and affects their function.