Inositol 1,4,5-trisphosphate A) binds to a specific site on protein kinase A. B) binds to a specific site on phosphoprotein phosphatase. C) is formed by three phosphorylations of inositol in the presence of ATP. D) regulates a Ca²⁺ channel in the endoplasmic reticulum.

Question

Quizplus · Accepted Answer

Inositol 1,4,5-trisphosphate (IP3) is a secondary messenger molecule that regulates the release of calcium ions from the endoplasmic reticulum via IP3 receptors. It binds to a specific site on the channel, causing it to open and release calcium ions into the cytoplasm. Therefore, choice D is the best answer. Choices A, B, and C are incorrect because they do not accurately describe the role or function of IP3.

Inositol 1,4,5-Trisphosphate