Iodide is transported out of the thyroid cells across the apical membrane into the follicle by a chloride-iodide ion counter- transporter molecule called pendrin.

TLS Online TPP Program

#Id: 6369

#Unit 2. Cellular Organization

When polymerase binding causes transition to the open complex and initiates transcription. This gives a low level of constitutive expression called the basal level.  Binding of RNA polymerase is the rate-limiting step in this case.

TLS Online TPP Program

#Id: 6370

#Unit 2. Cellular Organization

Lac repressor binds as a tetramer to two operators.

TLS Online TPP Program

#Id: 6371

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 6372

#Unit 2. Cellular Organization

lacZ encodes for b-galactosidase,a tetramer of 500 kD. The enzyme breaks lactose is cleaved into glucose and galactose.  This enzyme also produces an important byproduct, b-1,6-allolactase.

TLS Online TPP Program

#Id: 6373

#Unit 2. Cellular Organization

The lac mRNA (as most mRNA is in bacteria) is extremely unstable and decays with a half-life of only 3 minutes.

TLS Online TPP Program

#Id: 6374

#Unit 2. Cellular Organization

B-1,6-allolactase is a true inducer of Lac operon which activates Lac ZYA gene expression by inhibiting Lac Repressor