Now, why exactly does the cell need to block the transcription of these mRNA molecules that code for the proteins that break down lactose? So this is because inside the cell, we have a high concentration of glucose. So we do not actually have to break down lactose because we have the glucose that we can use as our energy source. And so because the concentration of glucose is high, we do not need to synthesize the proteins, the enzymes that are involved in the breakdown of lactose. So once again, this takes place because at high concentration of glucose, the cell does not need to use lactose as the energy source because it has the glucose in the first place. And so the genes for our beta Galactosidase, as well as these other two genes, the proteins involved in the breakdown of lactose are essentially turned off.