Ion channels can be opened or closed via three signal transduction mechanisms. Two of them are extracellular signals and second messengers. What is the third mechanism for opening or closing ion channels?

Answer:G protein action

Explanation:

Signal transduction through protein action is through G protein coupled receptors (GPCR). Binding of different types of signal molecules to G protein couple receptors is a general mechanism of signal transduction.

G proteins act as an intermediary to a stimulation of a receptor. When an extracellular messenger, the hormone (H) combines with the specific receptor (R) on the plasma membrane. The H-R complex activates the regulatory components of G proteins. The G-protein inturn will interact with the effect proteins which may be enzymes or ion channel proteins, which result in the desired effect.