It is the action of the repressor that defines the lac operon as an inducible system. In order to understand how the system works, it is important to understand how the repressor functions. Clicking on each of the thumbnail images will bring up a larger, labeled version of the described scene.

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	The lac operon functions inside a bacterial cell. This is a simplified bacterial cell.
	An operon is a series of genes linked together on the bacterial chromosome that are activated by a single promoter and produce a single mRNA molecule.
	Expression of the genes is turned off when a protein called the repressor binds to the promoter (red) and operator (orange) of the operon.
	Lactose must be added to to activate the lac operon. Here it is seen outside of the cellular membrane.
	Some of the lactose enters the cell passively and binds to the repressor molecule.
	The repressor will only be removed when it is bound with lactose.

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