Signal transduction is part of a cell's response to an external signal. Although signal transduction pathways can differ in their details, there are some common elements. Determine which of the statements below accurately describe signal transduction pathways. Select the six correct statements. A ligand, such as a hormone, binds to a specific cell surface receptor on a target cell. Phosphatases remove phosphoryl groups from polypeptides, regulating a cell's response. A ligand phosphorylates protein residues, ending the signaling cascade inside the cell. A second messenger carries a signal from a tissue or organ to a target cell. A receptor changes conformation upon binding, transmitting a signal across the cell membrane. A second messenger may carry a signal from the cell membrane to an organelle. Signal transduction cascades directly transmit a single stimulus to a single target. A receptor may pass on a signal by interacting with another protein or by acting as an enzyme. Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly.
