Question

There are two basic forms of cytoplasmic signaling one uses ____ and the other uses _____

Answer 1

There are two basic forms of cytoplasmic signalling; one uses cell surface receptors and the other uses cytoplasmic receptors. Cell surface receptors are present on the surface of plasma membrane and are activated by hydrophilic ligand molecules (that cannot cross plasma membrane) such as hormone insulin. The largest class of cell surface receptors are G-protein coupled receptors (GPCR) that upon activation initiate the cytoplasmic signalling via secondary messenger, cAMP. Intracellular receptors, on the other hand, are present in the cytosol or inside the nucleus and are activated by hydrophobic ligand molecules (that can cross plasma membrane) such as steroid hormones. Intracellular receptors may directly act as transcriptional factors and bind to their respective response elements on DNA to regulate gene expression.