Catalyzes calcium-induced ATP-independent rapid bidirectional and non-specific movement of the phospholipids (lipid scrambling or lipid flip-flop) between the inner and outer membrane of the mitochondria (PubMed:14573790, PubMed:17226776, PubMed:18358005, PubMed:29337693, PubMed:31769662). Plays an important role in mitochondrial respiratory function, morphology, and apoptotic response (PubMed:12649167, PubMed:14573790, PubMed:17226776, PubMed:18358005). Mediates the translocation of cardiolipin from the mitochondrial inner membrane to outer membrane enhancing t-Bid induced cytochrome c release and apoptosis (PubMed:14573790, PubMed:17226776, PubMed:18358005). Enhances TNFSF10-induced apoptosis by regulating the distribution of cardiolipin in the mitochondrial membrane resulting in increased release of apoptogenic factors and consequent amplification of the activity of caspases (PubMed:18491232). Regulates cardiolipin de novo biosynthesis and its resynthesis (PubMed:16939411). {ECO:0000269|PubMed:12649167, ECO:0000269|PubMed:14573790, ECO:0000269|PubMed:16939411, ECO:0000269|PubMed:17226776, ECO:0000269|PubMed:18358005, ECO:0000269|PubMed:18491232, ECO:0000269|PubMed:29337693, ECO:0000269|PubMed:31769662}. This is the function of Ensembl gene identifier ENSG00000187838 (PLSCR3, phospholipid scramblase 3).