During apoptosis, the recognition and phagocytosis of apoptotic cells by macrophages is triggered by the externalization of a specific phospholipid. Which molecule is flipped from the inner to the outer leaflet of the plasma membrane to serve as an eat me signal?

• A Sphingomyelin
• B Phosphatidylcholine
• C Phosphatidylethanolamine
• D Phosphatidylserine ✓

Explanation

In viable cells, phosphatidylserine is restricted to the inner leaflet of the plasma membrane. During apoptosis, caspases inhibit flippase and activate scramblase, causing phosphatidylserine to externalize. This acts as an eat me signal for macrophages. Phosphatidylcholine and sphingomyelin are primarily outer leaflet lipids. Phosphatidylethanolamine is also internalized but is not the primary recognition signal for phagocytosis.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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