Uniporter

Uniporter

A uniporter is a type of membrane transport protein that facilitates the movement of a single type of molecule or ion across a cell membrane. Unlike other transport proteins, uniporters do not couple the transport of the molecule to the movement of another molecule or ion. This process is known as facilitated diffusion, and it allows substances to move down their concentration gradient without the input of energy.

Diagram of different types of transporters, including uniporters.

Mechanism

Uniporters operate by binding to the specific molecule they transport, undergoing a conformational change, and releasing the molecule on the other side of the membrane. This process is driven by the concentration gradient of the molecule, meaning that the molecule moves from an area of higher concentration to an area of lower concentration.

Illustration of facilitated diffusion through a cell membrane.

Examples

One well-known example of a uniporter is the glucose transporter found in the membranes of many cells. This transporter allows glucose to enter the cell where it can be used for energy production.

Diagram of glucose transport and metabolism in a cell.

Structure

Uniporters are typically composed of multiple transmembrane domains that form a channel or pore through which the molecule can pass. The structure of these proteins is crucial for their specificity and function.

Structure of a protein involved in transport.

Function in Cells

Uniporters play a critical role in maintaining cellular homeostasis by regulating the internal concentration of various molecules. They are involved in numerous physiological processes, including nutrient uptake, ion balance, and signal transduction.

Related Transport Mechanisms

Uniporters are one of several types of transport proteins. Others include:

• Symporters, which transport two different molecules in the same direction.
• Antiporters, which transport two different molecules in opposite directions.

Related Pages

• Facilitated diffusion
• Membrane transport protein
• Glucose transporter

References

• Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). Molecular Biology of the Cell. 4th edition. New York: Garland Science.
• Lodish, H., Berk, A., Zipursky, S. L., Matsudaira, P., Baltimore, D., & Darnell, J. (2000). Molecular Cell Biology. 4th edition. New York: W. H. Freeman.