Hormonal action depends on whether the hormone is Lipid or water soluble. Lipid soluble hormones can cross the target cell membrane easily, get attached to the mobile receptors within the cytoplasm and reach the nucleus to perform their functions. However water soluble hormones are proteinaceous and these include insulin, oxytocin etc. These cannot cross the cell membrane easily. These get attached to the static receptors on the cell membrane. This attachment triggers the formation of secondary messengers that help these hormones to act on cells. These also cause amplification of hormonal action so that many targets are affected by single hormone. This concept was explained by Sutherland. Secondary messengers commonly seen in cells are Cyclic AMP. Other examples are Inositol tri phosphate (IP3), Calcium and Cyclic GMP.