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Phosphatidylinositol and Signal Transmission

BIOCHM-BHGVMW

Phosphatidylinositol can be phosphorylated to produce phosphatidylinositol 4,5-bisphosphate ($PIP_2$). A variety of signaling molecules can stimulate Phospholipase C to degrade $PIP_2$ into inositol 1,4,5-trisphosphate ($IP_3$) and diacylglycerol (DAG).

Which choice describes the role that $IP_3$ plays in the cell?

A

$IP_3$ directly stimulates the release of $Na^+$ ions from several organelles.

B

$IP_3$ directly stimulates the release of sequestered $Ca^{2+}$ from the endoplasmic reticulum.

C

$IP_3$ directly stimulates the re-uptake of $Ca^{2+}$ into the endoplasmic reticulum.

D

$IP_3$ binds directly to protein kinase C (PKC) causing it to become active.

E

$IP_3$ binds directly to protein kinase C (PKC) causing it to become inactive.