the lactose (lac) operon in E. coli is a gene that helps break down lactose in a cell. if there is no lactose present, the operon is repressed. in 3-5 sentences, explain how the lac operon is used and repressed in cells.

The lac operon in E. coli functions to regulate the metabolism of lactose, allowing the bacteria to utilize this sugar as an energy source when present. When lactose is absent, a protein called the lac repressor binds to the operator region of the operon, blocking RNA polymerase from transcribing the genes required for lactose metabolism, thus keeping the operon repressed. However, when lactose is available, some of it is converted to allolactose, which binds to the repressor and causes it to change shape, releasing it from the operator. This derepression allows RNA polymerase to transcribe the genes needed for lactose uptake and breakdown, enabling the cell to metabolize lactose effectively.