What is the lac operon?

Do you know anyone with lactose intolerance? Lactose is a sugar molecule found in dairy products like milk, cheese, yogurt, or ice cream. Lactose is made of a galactose molecule and a glucose molecule linked together. If a person is lactose intolerant, that means they cannot break down or digest that sugar.
Some bacteria can digest lactose and use it for an energy source. What helps them accomplish this? The lac operon. An operon is a set of genes that are regulated and expressed as a package deal. You can think of them as a team, working together towards a common goal. The genes will code for proteins that carry out certain functions. In this case, the team is helping digest and metabolize lactose. Escherichia coli, among other species, have a lac operon. In E. coli, the lac operon consists of three genes: lacZ, lacY, and lacA. LacZ codes for the protein beta-galactosidase, lacY codes for lactose permease, and lacA codes for transacetylase.

Lactose permease brings the lactose molecule into the cell in the same direction as the proton gradient. From there, beta-galactosidase breaks apart the lactose into two molecules- the glucose and galactose. Transacetylase takes out any dangerous by-products left over after the metabolic process. Who would have thought a microorganism could carry out such interesting cellular activities?