Carrier protein

Carrier protein is a type of protein that facilitates the transport of specific substances across a cell membrane. These substances can include ions, small molecules, and large macromolecules, which cannot cross the lipid bilayer due to their size, charge, or polarity. Carrier proteins are integral membrane proteins; that is, they exist within and span the membrane across which they transport substances.

Function

Carrier proteins bind to molecules and change shape to shuttle them across the membrane. They are often (though not always) transmembrane proteins. A carrier protein is required to move particles against a concentration gradient. This process is called active transport.

Types of Carrier Proteins

There are several types of carrier proteins that are specialized for certain types of molecules. These include:

• Ion channels: These proteins allow specific ions to pass through the membrane.
• Uniporters: These proteins transport a single type of molecule in one direction.
• Symporters: These proteins transport two different types of molecules in the same direction.
• Antiporters: These proteins transport two different types of molecules in opposite directions.

Role in Disease

Mutations in carrier proteins can lead to diseases such as cystic fibrosis, where a mutation in the CFTR chloride channel leads to a buildup of mucus in the lungs, or phenylketonuria, where a mutation in the carrier protein for the amino acid phenylalanine leads to a buildup of phenylalanine in the body.

See Also

• Membrane transport protein
• Facilitated diffusion
• Active transport
• Passive transport