Key Takeaways

KEY TAKEAWAYS

• Cell signaling can involve cell to cell connections, paracrine, autocrine, or endocrine signaling. • Ligands can be extracellular or intracellular, depending on where they bind. The most hydrophobic ligands will be intracellular. • Signaling pathways can turn on genes, turn off genes, affect cellular metabolism, or affect transcription. • Calcium, phosphatidyl inositol, and cyclic AMP are common intracellular second messengers. • G protein-coupled receptors are a large family of receptors that involve many different activities in eukaryotic cells only.