Sugar Concentration

Varying sugar concentrations within and outside the cell.

Lactose Exterior:

Glucose:

Lactose Interior:

Allolactose:

Promoter

Promotes the transcription of lacZ and LacY

Operator

A binding site for Repressor, which can Repress transcription of lacZ and lacY

Repressor

A protein that binds to the operator and prevents transcription of LazZ and LacY

Permease (LacY)

A membrane protein that speeds the transport of lactose into the cell

Beta-Galactosidase (LacZ)

An enzyme binds lactose and catalyzes its conversion into allolactose and glucose which will be eventually metabolized into energy.

CAP-cAMP

The Catabolite Activator Protein (CAP) essentially detects low glucose conditions. CAP complexs with cAMP, which induces it bind upstream of the lac operon and increases its transcription. To simplify the graphs for new users, we have set CAP to default to Inactive. When you are ready to think about CAP function, modify it to Active and notice and the difference(s).

Plasmid

Selecting Plasmid will introduce a second copy of the lac operon (on a plasmid) to the cell, making a merodiploid cell. This technique was classically used determine if a certain mutation can influence expression on other pieces of DNA or not. This is known as the ‘cis trans test’.