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Multiple Choice
Which second messenger causes the release of calcium ions ($\mathrm{Ca^{2+}}$) from the endoplasmic reticulum?
A
Cyclic adenosine monophosphate (cAMP)
B
Diacylglycerol (DAG)
C
Inositol 1,4,5-trisphosphate (IP$_3$)
D
Guanosine triphosphate (GTP)
Verified step by step guidance
1
Understand the role of second messengers: Second messengers are molecules that relay signals received by receptors on the cell surface to target molecules inside the cell. They play a critical role in signal transduction pathways.
Identify the second messenger responsible for calcium ion ($\mathrm{Ca^{2+}}$) release: Among the options provided, the second messenger that directly triggers the release of calcium ions from the endoplasmic reticulum is Inositol 1,4,5-trisphosphate (IP$_3$).
Explain how IP$_3$ works: IP$_3$ is produced when a signaling molecule activates a receptor, which in turn activates phospholipase C. Phospholipase C cleaves a membrane phospholipid (PIP$_2$) into two products: diacylglycerol (DAG) and IP$_3$.
Describe the action of IP$_3$: IP$_3$ binds to IP$_3$ receptors on the membrane of the endoplasmic reticulum. This binding opens calcium channels, allowing $\mathrm{Ca^{2+}}$ ions to flow from the endoplasmic reticulum into the cytoplasm.
Summarize the importance of $\mathrm{Ca^{2+}}$ release: The increase in cytoplasmic $\mathrm{Ca^{2+}}$ concentration acts as a signal for various cellular processes, such as muscle contraction, secretion, and cell signaling pathways.