The Lac Operon

Lactose = Galactose and Glucose

Cells adapt to their environment by turning on and off genes. An operon is a cluster of bacterial genes + adjacent promoter that controls the transcription of those genes.

A promoter = doorknob. It is kin to other operons. An operator is like the keyhole in a doorknob that is only unlocked by a specific key. specific key= regulatory protein.

NO LACTOSE

Lactose Present

When the enzymes produced, they break down lactose and allolactose, then release the repressor to stop transcription.

E. Coli prefer glucose

When both glucose and lactose, genes for lactose metabolism are transcribed to a small extent.

Maximal transcription occurs only when glucose is absent and lactose is present. The action of cyclic AMP and a catabolite activator protein produce this effect.

a permease that transports lactose across the membrane beta-galactosidase which hydrolyzes lactose into glucose and galactose. a transacetylase ????? uncertain.