Lac operon

What is E. coli?

A bacterium that respires glucose but also respires lactose if glucose is not available

What does the bacteria need to do to respire lactose?

Produce new enzymes - the genes required for these enzymes are found on the lac operon

What are the 3 structural genes and what do they do?

Z, Y and A, produce enzymes that help the bacterium digest lactose

What is B-galactosidase?

Helps bacteria break down lactose

What does lactose permease?

Makes cell wall more permeable to the lactose

What does the regulatory gene (Lacl) produce in the presence of glucose?

Lac repressor protein which is a transcription factor that binds to the operator site

What does the repressor protein produced by Lacl do?

Blocks the RNA polymerase form transcribing the genes by binding to the promoter region, so the enzymes aren’t transcribed

What does lactose do to the repressor?

Binds to the repressor on an allosteric site which changes its shape, so it is prevented from binding to the operator. This means RNA polymerase can start transcription