What does the lac operon in E. coli regulate?

The lac operon in E. coli is a well-studied example of gene regulation that specifically controls the uptake and breakdown of lactose. This system consists of structural genes that encode proteins necessary for the transport of lactose into the bacterial cell and the enzymes required to metabolize it. When lactose is available, it acts as an inducer that binds to the repressor protein, allowing transcription of the genes involved in lactose utilization. This regulation enables the bacterium to efficiently use lactose as an energy source when other preferred sources, such as glucose, are not present.

In contrast, options related to glucose metabolism, protein synthesis, or fatty acid synthesis do not correctly describe the function of the lac operon. The operon is primarily focused on lactose and does not directly regulate these other metabolic pathways. Thus, identifying the correct role of the lac operon is essential for understanding how E. coli adapts to different nutrient conditions.