lac operon WTFFFFFFFFFFFFFFFFFFFF?

What exactly about it don't you get? I could probably help you better that way.

what do the words mean?

The lac operon is an example of an operon - which is a length of DNA that is made up of two parts, a structural gene and two control sites

The structural genes code for proteins and enzymes, the control sites are made up of the "operator" and "promoter" regions.

The Operator region is a length of DNA that has the ability to activate genes (and allow them to create proteins/enzymes) and disactivate them.
The Promoter region is a length of DNA that RNA polymerase binds to when transcription needs to begin.

The best example of an operon in use is the lac operon, which is best demonstrated in E. Coli. This is because it uses glucose for respiration normally, but it can use lactose if glucose is absent. If E. Coli is placed in a culture of lactose, it needs to quickly produce large amounts of two enzymes (Beta-galactosidase and lactase permease), so it can metabolise lactose.

So, if you've got the OCR textbook, you should be able to see a diagram of the lac operon. It'll have a Regulator gene, region of RNA polymerase, followed by the Operator region, Promoter region, and finally the structural genes (Beta-galactosidase and lactase permease). The Regulator gene and RNA polymerase are not part of the operon itself, but are crucial to it's function.

The regulator gene synthesises a "repressor protein". This protein has two binding sites - one for lactose and one for the Operator region.

If lactose is absent, the repressor protein binds to the Operator region, and in turn covers part of the Promoter region.
As a result, the RNA polymerase cannot attach to the operon, so the two enzymes cannot be synthesised.

If lactose is present, the repressor protein can bind to the lactose. The lactose acts as a non-competitive inhibitor, changing the shape of the repressor protein and causing it to dissociate from the operator region.
Therefore, RNA polymerase attaches to the operon and allows Beta-galactosidase and lactase permease to be synthesised, and E. Coli can metabolise lactose.

Woow.
thanks