text: user12686: Is ligand a type of protein or vice versa?
  
  user15618: A ligand is any molecule that can bind to a receptor. A receptor is always a protein. A ligand can be a protein, but also something else, be it a combination of protein with carbohydrates and-or fats, or just molecules such as cyclic AMP, any chemical compound, structures expressed on the cell surface, pretty much any structure you can think of.
  
original_text: 12686: <p>Is ligand a type of protein or vice versa?</p>
   15618: <p>A ligand is any molecule that can bind to a receptor. A receptor is always a protein. A ligand can be a protein, but also something else, be it a combination of protein with carbohydrates and-or fats, or just molecules such as cyclic AMP, any chemical compound, structures expressed on the cell surface, pretty much any structure you can think of.</p>
  