1. Adrenaline has four functional groups and a much smaller carbon skeleton . The polar functional groups dominate in determining the characteristic of the molecule making it polar so this makes the epinephrine unable to pass through the cell membrane . 2.G-proteins is also known as guanine – binding proteins and acts as a molecular switches inside cells and these regulates the metabolic enzymes , transporter proteins and other ions channels . G proteins helps in other diverse systemic functions .3.Receptor tyrosine kinases activates the G- proteins.