Which of the following statements is TRUE? A) Phosphorylation by protein kinases can stimulate or inhibit the activity of effector proteins. B) Ca²⁺ is not a second messenger. C) Phosphodiesterase converts GMP into cGMP D) Conversion of ATP to cAMP is a phosphorylation reaction. E) Phospholipase C converts ATP to cAMP.

Question

Quizplus · Accepted Answer

Phosphorylation by protein kinases can either activate or inhibit the activity of effector proteins, depending on the specific target and context. This is a key mechanism of signal transduction in cells. Choice B is not a valid statement as Ca²⁺ is not a recognized molecule. Choice C is not correct, as phosphodiesterase converts cAMP to AMP, not GMP to cGMP. Choice D is also incorrect, as conversion of ATP to cAMP is a dephosphorylation reaction, not a phosphorylation reaction. Choice E is not correct, as phospholipase C cleaves membrane phospholipids to produce second messengers such as inositol triphosphate and diacylglycerol, not cAMP.

Which of the Following Statements Is TRUE