And when this happens is we actually lose these stabilizing interactions here and these stabilizing interactions here, as shown in this particular case. So basically, the polar head does not actually want to interact and cannot interact in a stabilizing way with that hydrophobic core of the membrane. And likewise, the non polar tail portion of the fossil lipid also cannot and does not want to interact with the water molecules of the aqueous environment. So we see that whenever a flip flop takes place, there is a certain amount of energy, a relatively large amount of energy that actually must be overcome. So there's a large energy barrier to this process. And that's because this process is energetically unfavorable.