Correct option is C
Explanation-
Option c: IP₃ is a small lipid-soluble molecule that binds to IP₃ receptor on plasma membrane thereby increasing Ca²⁺ concentration in the cytosol.
IP₃ (Inositol 1,4,5-trisphosphate) is generated when PIP₂ is hydrolyzed by activated PLC-β. IP₃ is water-soluble (NOT lipid-soluble). It diffuses through the cytosol to the endoplasmic reticulum (ER). There, it binds to IP₃ receptors, which are ligand-gated calcium channels located on the ER membrane, not the plasma membrane. This binding causes release of Ca²⁺ from ER into the cytosol, raising intracellular calcium levels. So, while IP₃ does increase Ca²⁺ concentration in the cytosol, the statement is incorrect in saying:
Thus, Option c is the INCORRECT statement, and marking it correct as the answer to the question.
Incorrect options (correct statements)
Option a: PLC-β acts on phosphatidyl inositol 4,5-bisphosphate (PIP₂), which is present in the inner half of the plasma membrane lipid bilayer.
This is correct. PIP₂ is a minor phospholipid located on the inner leaflet of the plasma membrane. PLC-β hydrolyzes PIP₂ into IP₃ and DAG.
Option b: Activated PLC-β cleaves the PIP₂ to generate two products: inositol 1,4,5-trisphosphate (IP₃) and diacylglycerol (DAG).
This is correct. PIP₂ → IP₃ (soluble) + DAG (membrane-bound).
Option d: DAG gets further cleaved to release arachidonic acid, which is used in the synthesis of eicosanoids including prostaglandins. DAG also activates Ca²⁺-dependent protein kinase C or PKC.
This is correct. DAG serves two major roles activates PKC (with help of Ca²⁺ and phosphatidylserine). DAG can be cleaved to release arachidonic acid, precursor for eicosanoids like prostaglandins.
Final Answer:
Correct answer to the question (i.e., incorrect statement): Option c
