Secondary active transport

Secondary active transport is a form of active transport across a biological membrane in which a transport protein couples the movement of an ion (typically sodium or hydrogen) down its electrochemical gradient to the movement of another molecule (the "secondary" solute) against its concentration gradient. This process is distinct from primary active transport, where energy from ATP is directly used to transport a solute against its concentration gradient.

Mechanism

Secondary active transport brings solute or ions into the cell (or out of the cell) along with the ion that is moving down its electrochemical gradient. The transport protein, or carrier, involved in secondary active transport is a symporter that moves both ions in the same direction, or an antiporter that moves ions in opposite directions.

Types

There are two types of secondary active transport:

• Cotransport (or symport): In cotransport, the direction of the actively transported ion's movement is the same as that of the solute being transported. An example of cotransport is the sodium-glucose transport protein.

• Countertransport (or antiport): In countertransport, the direction of the actively transported ion's movement is opposite to that of the solute being transported. An example of countertransport is the sodium-calcium exchanger.

Examples

Examples of secondary active transport systems include the sodium-potassium pump, the Sodium-calcium exchanger, and the sodium-glucose cotransporter.

See also

• Active transport
• Primary active transport
• Cotransport
• Countertransport

Secondary active transport Resources
Latest articles Most recent articles Ongoing trials	Wikipedia