This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following phospholipid serves as a marker of apoptosis 
Select and explain. 
A. Phosphatidylinosital, B. Phosphatidyl serine, C. Phosphatidyl choline, D. Phosphatidyl ethanolamine
B: Phosphatidyl serine
Answer: B: Phosphatidyl serine 
Explanation: Phosphatidyl serine is normally present on inner mitochondrial membrane, flipping of it to the outer mitochondrial membrane is seen in apoptosis.