11.2 Cell Communication

G Protein-Coupled Receptors Loosely attached to the cytoplasmic side of the membrane. The G protein functions as a molecular switch that is either on or off depending on which 2 guanine nucleotides is attached. Then the G protein is activated when GPD is bounded to it .

The activated G-protein moves away from the receptor, diffuses alone the membrane and then binds to an enzyme. When the enzyme gets activated, cellular response starts

3RD STEP G-protein leaves the enzyme, which returns to its original state. The GTPase function of the G-protein allows the pathway to shut down rapidly when the signaling molecule is no longer present

Receptor Tyrosine Kinases

Ion Channel Receptors

When the ligand binds to the receptor and the gate opens, specific ions can flow through the channel and rapidly change the concentration of that particular ion inside the cell. This change may directly affect the activity of the cell in some way.

When the ligand dissociates from this receptor, the gate closes and ions no longer enter the cell.

Steroid hormone interacting with an intracellular receptor