The lacY gene is part of the lac operon, a set of genes found in Escherichia coli that are involved in the metabolism of lactose. Specifically, lacY encodes for the lactose permease protein, which facilitates the transport of lactose into the bacterial cell. This process is essential for the bacteria to utilize lactose as an energy source. Lactose permease functions by using a proton gradient to move lactose across the cell membrane. When lactose enters the cell, it can be broken down into glucose and galactose, which can then be used in cellular respiration. The regulation of lacY is crucial for the efficient use of lactose in environments where it is available.