The permeases are membrane transport proteins, a class of multipass transmembrane proteins that facilitate the diffusion of a specific molecule in or out of the cell

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 by passive transport

Passive transport

Passive transport means moving biochemicals and other atomic or molecular substances across membranes. Unlike active transport, this process does not involve chemical energy, because, unlike in an active transport, the transport across membrane is always coupled with the growth of entropy of the...

. In contrast, active transporters

Active transport

Active transport is the movement of a substance against its concentration gradient . In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose, and amino acids. If the process uses chemical energy, such as from adenosine...

 couple molecule transmembrane transport with an energy source such as ATP or a favorable ion gradient.

See also

• Lactose permease
  Lactose permease
  Lactose permease has a structure that consists of two halves, each of which comprises six membrane-spanning alpha helices.The two halves are well separated and are joined by a single stretch of polypeptide....
  
  
• Beta-galactoside permease
  Beta-galactoside permease
  β-galactoside permease is a membrane-bound transport protein that pumps lactose into the cell....
  
  

It was originally discovered in the 1930s by Joy Adames. It is a transporter protein that helps in various aspects of cellular life including DNA replication, translation of RNA, and diffusion.

• Amino acid permease
  Amino acid permease
  Amino acid permeases are membrane permeases involved in the transport of amino acids into the cell. A number of such proteins have been found to be evolutionary related...
  
  

External links

• • - Calculated spatial positions of permeases in membrane