Molecular And Cellular Biology Exam 1 Practice

What is the role of second messengers like IP3 and DAG in phospholipase C signaling?

IP3 and DAG are second messengers, but they do not influence calcium release or PKC. PLC cleaves PIP2 to IP3 and DAG, which release Ca2+ and activate PKC. IP3 directly activates PKC; DAG releases Ca2+. IP3 and DAG are not part of PLC signaling.

Correct Answer:

PLC cleaves PIP2 to IP3 and DAG, which release Ca2+ and activate PKC.

Explanation:

PLC signaling generates two second messengers, IP3 and DAG, which coordinate calcium release and PKC activation. When PLC cleaves PIP2 in the inner plasma membrane, it produces IP3, a soluble molecule that diffuses through the cytosol to bind receptors on the endoplasmic reticulum and open Ca2+ channels. This raises cytosolic Ca2+, enabling many Ca2+-dependent processes. The other product, DAG, remains in the membrane and, together with the Ca2+ rise, activates protein kinase C (PKC) by helping recruit PKC to the membrane and promoting its catalytic activity. Thus, IP3’s role is to release Ca2+, while DAG helps activate PKC; both arise from PLC-mediated cleavage of PIP2.

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