G-Proteins are a group of proteins that act as molecular switches inside cells. They play a crucial role in transmitting signals from outside the cell to its interior, helping to regulate various cellular processes. When a signal molecule, such as a hormone, binds to a receptor on the cell surface, it activates the G-Protein, which then interacts with other proteins to initiate a response. These proteins are classified into three main types: Gs, Gi, and Gq, each with distinct functions. Gs proteins stimulate cellular activity, while Gi proteins inhibit it. Gq proteins activate pathways that lead to increased levels of calcium ions, influencing various physiological responses.