When the glucose concentration is low the cell must actually metabolize some other type of biological molecule. And one other common type of biological molecule that the cell metabolizes is lactose. So lactose is a sugar molecule. It's a disaccharide that consists of two individual sugar monomers. So our lactose consists of a glucose as well as a galactose. Now, the enzyme that actually catalyzes the breakdown of lactose into glucose is known as betagalactosidase and betagalactosidase is basically controlled.