Activated phospholipase C cleaves a membrane-bound phospholipid into which two molecules?
ADiacylglycerol and inositol triphosphate
BCyclic AMP and adenosine triphosphate
CInositol triphosphate and cyclic AMP
DDiacylglycerol and adenosine triphosphate
Answer & Solution
Correct answer: A. Diacylglycerol and inositol triphosphate
1. Some water-soluble hormones use calcium ions rather than cAMP as the second messenger.
2. In that system the G protein activates phospholipase C instead of adenylyl cyclase.
3. Phospholipase C splits a membrane-bound phospholipid into diacylglycerol and inositol triphosphate.
4. Diacylglycerol activates protein kinases and starts a phosphorylation cascade, just as cAMP does.
5. Inositol triphosphate frees calcium ions from cytosolic stores such as the smooth endoplasmic reticulum.
6. Cyclic AMP belongs to the other pathway and adenosine triphosphate is the substrate that adenylyl cyclase converts, so neither is a cleavage product here.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 17 "The Endocrine System", section 17.2 Hormones_
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