Step number two is now that the epinephrine is released, it travels through the bloodstream. Eventually it diffuses into the extracellular matrix around the cells and then it binds until specific receptor transmembrane proteins found on the membranes of those cells. So the primary messenger locates and attaches onto a receptor which are usually transmembrane proteins. These receptors have an extracellular component found outside the cell and an intracellular component found inside the cell. And that ligand, that primary messenger shoulder red actually binds onto the outside portion of that transmembrane protein, the receptors. So this is the membrane, the outside the cell, the inside the cell.