Signaling molecules with cell surface receptors

Hydrophilic  (water-soluble)  molecules  (that cannot diffuse across the hydrophobic   interior  of  the  lipid  bilayer)  bind  to  receptors   in  the  plasma membrane. These involves the peptide hormones, like as insulin and glucagon, and the small charged  molecules,  frequently biogenic  amines,  like as epinephrine (adrenalin)  and histamine,  which are derived  from amino acids and function  as neurotransmitters and hormones. Some lipophilic (lipid-soluble) hormones also bind to receptors located in the plasma membrane. These involve the prostaglandins, a family of structurally same compounds which are found in both vertebrates and invertebrates.  The Prostaglandins  are synthesized  from arachidonic  acid  a  20-carbon  fatty  acid  with  four  unsaturated  double  bonds and act as paracrine signaling molecules. Other antiin?ammatory and Aspirin agents inhibit the synthesis of prostaglandins.