Question

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. Select the six statements that accurately describe signal transduction pathways.1. A receptor changes conformation upon binding, transmitting a signal across the cell membrane.2. Signal transduction cascades, often involving protein kinases, amplify a signal intracellularly.3. Signal transduction cascades directly transmit a single stimulus to a single target.4. A second messenger may carry a signal from the cell membrane to an organelle.5. A ligand, such as a hormone, binds to a specific cell surface receptor on a target cell.6. A ligand phosphorylates protein residues, ending the signaling cascade inside the cell.7. A receptor may pass on a signal by interacting with another protein or by acting as an enzyme.8. Phosphatases remove phosphoryl groups from polypeptides, regulating a cell's response.9. A second messenger carries a signal from a tissue or organ to a target cell.

Answer 1

Answer:

1. 2. 4. 5. 7 and 8

Explanation:

3. False: A single stimulus can activate multiple target cells.

6. False: A ligand does not phosphorylate protein residues but can bind and activate kinase receptors resulting in conformational changes that induce intracellular phosphorylation of target protein domains.

9. False: Second messengers relay stimulus to intracellular targets. e.g calcium can act as a second messenger.