Phospholipid scramblase 1 (PLSCR1) is a protein that plays a crucial role in the movement of phospholipids between the inner and outer layers of cell membranes. This process is important for various cellular functions, including cell signaling and apoptosis, as it helps maintain membrane integrity and fluidity. PLSCR1 is activated in response to specific signals, such as calcium ions, which trigger the scrambling of phospholipids. This action disrupts the normal asymmetry of the membrane, allowing for the exposure of certain molecules that can signal other cells or initiate programmed cell death.