63. Which of the following statements about G-protein-coupled receptors (GPCRs) is false? GPCRs are the largest family of cell-surface receptors in humans. GPCRs are used in endocrine, paracrine, and neuronal signalling. GPCRs are found in yeast, mice, and humans. The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.