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: 5528

#Unit 7. System Physiology – Animal

Late proximal tubule reabsorbs primarily NaCl

TLS Online TPP Program

#Id: 5529

#Unit 7. System Physiology – Animal

In late proximal convoluted tubule High tubular fluid Cl− concentration is the driving force for reabsorption

TLS Online TPP Program

#Id: 5530

#Unit 7. System Physiology – Animal

Function of the two exchangers is to transport NaCl from the lumen into the cell:

Na+-H+ exchanger

Cl−-formate− anion exchanger

TLS Online TPP Program

#Id: 5531

#Unit 7. System Physiology – Animal

Transepithelial Voltage 

Cl− diffusion establishes a Cl− diffusion potential, making the lumen positive with respect to blood.

TLS Online TPP Program

#Id: 5532

#Unit 7. System Physiology – Animal

Thin descending and thin ascending segments, have thin epithelial membranes with no brush borders, few mitochondria, & minimal levels of metabolic activity.

TLS Online TPP Program

#Id: 5533

#Unit 7. System Physiology – Animal

Descending part of the thin segment is highly permeable to water and moderately permeable to most Solutes (urea and sodium)