Now, let's move on to property number three that all these four have in common. And that's the fact that all of these different pathways depend on the correct interaction between protein molecules and other molecules in that pathway. So within any signal transduction pathway, proteins interact with other molecules. These other molecules can be proteins or they can be lipids or they can be secondary menstrual molecules such as the calcium ions. And these interactions basically stimulate and pass down the information needed to ultimately stimulate the cellular processes that lead to some particular type of physiological effect. So in the case of this pathway, physiological effect might be running away in the case of this pathway.