Which of the Following Statements Is True of Signal Molecules

question 12

Multiple Choice

Which of the following statements is true of signal molecules?

• A) When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules.
• B) In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP₃ and calcium.
• C) In most cases, signal molecules interact with the cell at the plasma membrane and then enter the cell and eventually the nucleus.
• D) Toxins such as those that cause botulism and cholera interfere with the ability of activated G proteins to hydrolyze GTP to GDP, resulting in phosphodiesterase activity in the absence of an appropriate signal molecule.
• E) Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.

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