Describe how the lac operon functions, and explain how it permits e. coli to produce the enzymes needed to break down lactose when it is present in the bacterium.

When the lac operon controls the expression of proteins in the E.coli cell that can break down lactose into two sugars, glucose and galactose. When lactose is present, it binds to the repressor that typically sits on the lac operon, changing the repressor's conformation such that it can no longer bind to the lac  operon. Because of this, RNA polymerase can now transcribe the gene into mRNA, which in turn is translated into the proteins that can break down lactose.

Leaves specifically the gas exchange between plants and the environment. while plants undergo photosynthesis, they also partake in cellular respiration. respiration is the process that happens in the leaves of plants.