Which of the following statements regarding signaling in normal cells and cancer
ID: 147622 • Letter: W
Question
Which of the following statements regarding signaling in normal cells and cancer cells is false? a. In normal cells, RTK transphosphorylation is strictly dependent on ligand binding. Ligand binding promotes a conformational change in the RTKs that is required for dimerization, and dimerization is required for transphosphorylation b, Cancers cells that over-express RTK's can respond to tiny amounts of ligand, and in some instances signaling can be ligand-independent. .Cancer cells that have established several autocrine signaling loops have a poor prognosis, because these cells have enabled multiple independent mitogenic signal transduction pathways. o d. The extracellular ectodomains of all RTKs are highly conserved in primary sequence and structure. Oe RTKs have a hydrophilic extracellular ectodomain, and hydrophobic transmembrane domain, and a hydrophilic cytoplasmic domain, which contains the catalytic portion of the protein.Explanation / Answer
ANSWER) D is false
The extracellular N terminal region contains a ligand-binding site which binds to extracellular ligands. It has a variety of conserved elements which include epidermal growth factor (EGF)-like domains, immunoglobulin (Ig)-like domains, fibronectin type III repeats, or cysteine-rich regions. These domains are characteristic for each subfamily of RTKs.
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All other options are true. RTK signaling is dependent on ligand binding, which induces dimerization. Phosphorylation helps bind GEF protein and Activate Ras protein downstream.
Cancers cells overexpressing RTKs can lead to ligand independent signaling due to conformational changes in RTK structure.
Cancer cells can use autocrine signaling to activate multiple transduction pathways which leads to poor prognosis.
RTKs have a hydrophilic Extracellular N terminal region, Transmembrane hydrophobic region, Intracellular Hydrophilic C-terminal region.
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