Final answer:
A G-Protein is part of a secondary messenger system that is activated by hormone binding to a receptor, subsequently generating second messengers like cAMP, DAG, and IP3 that mediate further intracellular signaling.
Step-by-step explanation:
A G-Protein falls under the class of a secondary messenger system. When a hormone binds to its membrane receptor, this activates the associated G-Protein by exchanging GDP for GTP. G-Proteins then induce the production of second messenger molecules, such as cyclic AMP (cAMP), diacylglycerol (DAG), and inositol 1,4,5-trisphosphate (IP3), which propagate the signal within the cell. This type of signaling is crucial in various physiological processes, including the regulation of metabolic enzymes and the control of ion channels.
The key role of G-Proteins in cell signaling is to act as a relay between the activated receptor and downstream effector molecules or enzymes such as adenylyl cyclase and phospholipase C. The activation of these enzymes leads to an increase in intracellular second messengers, which ultimately results in a variety of cellular responses.