1. What are the three phases of a signaling event? What kinds of molecular event
ID: 85084 • Letter: 1
Question
1. What are the three phases of a signaling event? What kinds of molecular events can occur during each phase?
2. All receptors are proteins. What effect does the receptor’s 3-D shape have on what ligand it can bind? What effect does ligand binding have on receptor’s 3-D shape? What changes occur to help the receptor transmit a signal? What problems might occur if the gene encoding a protein was mutated, such that the 3-D shape of the receptor was altered?
3. What are the different chemical forms that ligands can take? What kind of chemical bonds mediate the interaction between a receptor and a ligand – is it a permanent, or temporary interaction?
Explanation / Answer
Answer:
1. There are three stages of cell signalling:
i. Reception: where the target cell detects a signalling molecule present in the exogenous environment.
ii. Transduction: the conversion of the signal to a form that can bring about a specific cellular response.
iii. Response: the specific cellular effect brought about by the signalling molecule.
Reception:
A signal molecule (ligand) binds to a receptor protein (receptor), causing it to change shape. The interaction between a ligand and receptor is highly specific. A conformational change in a receptor is often the initial stage in the transduction of a signal. Receptors are found in two places:
a. Intracellular proteins are found inside the plasma membrane in the cytoplasm or nucleus. The signalling molecule must cross the plasma membrane and therefore must be hydrophobic (for instance the steroid hormone testosterone), or very small (Nitric Oxide).
b. Cell-surface proteins are embedded in the plasma membrane, and these receptors bind to water-soluble ligands.
Transduction:
Cascades of molecular interactions relay signals from receptors to target molecule in the cell. Signal transduction pathways often involve a phosphorylation cascade. Because the pathway is usually a multistep one, the possibility of greatly amplifying the signal exists.
At each step, enzymes called protein kinases phosphorylate and thereby activate many proteins at the next level. This cascade of phosphorylation greatly enhances the signal, allowing for a large cellular response. Not all components of signal transduction pathways are proteins, some are small non-protein water-soluble ions called second messengers, for example cyclic AMP.
Response:
Cell signalling leads to the regulation of transcription or cytoplasmic activities. Many signalling pathways ultimately affect protein synthesis, usually by turning specific genes on or off within the nucleus.
Often, the final activated molecule in a signalling pathway functions as a transcription factor. In the cytoplasm, signalling pathways often regulate the activity of proteins rather than their synthesis. For example, the final step in the signalling pathway may affect the activity of enzymes or cause cytoskeleton rearrangement.
(Since there are more than 1 question, the first full question have been answered according to the rules of Chegg)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.