Active transport

Active transport is a process that moves molecules and ions across cell membranes from a region of lower concentration to a region of higher concentration. This process is against the concentration gradient, and thus requires energy, typically in the form of ATP.

Overview

Active transport is a fundamental process in biology, enabling cells to maintain internal concentrations of small molecules that differ from concentrations in the external environment. It is one of the two main types of transport that involve the transfer of substances across a membrane, the other being passive transport.

Types of Active Transport

There are two types of active transport: primary and secondary.

Primary Active Transport

In primary active transport, the proteins involved get energy directly from the breakdown of ATP. An example of this is the sodium-potassium pump, which exchanges sodium ions for potassium ions across the plasma membrane of animal cells.

Secondary Active Transport

In secondary active transport, also known as co-transport, energy is used to transport molecules across a membrane indirectly. This involves the simultaneous movement of a second substance down its concentration gradient.

Role in Cells

Active transport is essential for many cellular functions, including uptake of cellular nutrients, removal of waste products, and ion transport necessary for the generation of action potentials in neurons.

See Also

• Passive transport
• Cell membrane
• Adenosine triphosphate
• Sodium-potassium pump