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.