Indicate true (T) and false (F) statements below regarding G-protein-coupled receptors (GPCRs). Your answer would be a five-letter string composed of letters T and F only, e. g. TTFFF. ( ) All GPCRs share a similar structure composed of seven transmembrane helices. ( ) All GPCR ligands (signal molecules) have a similar structure. ( ) GPCRs have only been found in multicellular organisms, consistent with their role in intercellular signaling. ( ) The hormone insulin is recognized by a GPCR on the surface of its target cells. ( ) Once activated, a GPCR molecule can activate multiple molecules of G protein to amplify the incoming signal.