<span style="color:rgb(20,20,20);background-color:rgb(254,254,254);">A cofactor is a non-protein chemical that assists with a biological chemical reaction. </span><br style="color:rgb(20,20,20);"/><br style="color:rgb(20,20,20);"/><span class='_lnk_exp' title='This link has since expired, or the site is not allowing us to check the link'>https://biologydictionary.net/cofactor/</span><br style="color:rgb(20,20,20);"/><span style="color:rgb(20,20,20);background-color:rgb(254,254,254);">Please explain the use of the prefix "non" vs "un" in "non-protein..." .</span><br style="color:rgb(20,20,20);"/><span style="color:rgb(20,20,20);background-color:rgb(254,254,254);">Why can't we use un protein?</span>