True about cardiolipin is all except

Cardiolipin (diphosphatidylglycerol) is a phospholipid present in mitochondria.   It is formed from phosphatidylglycerol, which in turn is synthesized from CDP-diacylglycerol and glycerol 3-phosphate. Cardiolipin, found in the inner membrane of mitochondria, has a key role in mitochondrial structure and function and is also thought to be involved in programmed cell death (apoptosis). Cephalin: Has choline base which has labile methyl group.   Harper's Illustrated Biochemistry 30th edition page no 248