What is Facilitated Diffusion?
Facilitated diffusion is a type of passive transport that allows molecules and ions to move across a cell membrane It is a type of carrier-mediated transport, meaning it utilizes proteins and other molecules to help move the substance from one side of the membrane to the other. Unlike simple diffusion, which happens spontaneously, facilitated diffusion requires energy from the cell.
Facilitated diffusion occurs when a molecule binds to a transporter protein on the cell membrane. The transporter protein changes shape, allowing the molecule to move through it and across the membrane. Once the molecule crosses the membrane, the transporter protein changes back to its original shape, trapping the molecule on the other side of the membrane.
The most common type of facilitated diffusion is called channel-mediated transport. This occurs when the transporter protein forms a channel, or hole, in the cell membrane. Substances can flow freely through the channel and move from one side of the cell membrane to the other. A second type of facilitated diffusion is called carrier-mediated transport. This occurs when the transporter protein binds to the substance, changes its shape, and transports it across the membrane.
Facilitated diffusion is a very important process in cells because it allows them to absorb essential substances, such as glucose and electrolytes, from the environment. It also helps the cells to release waste products, such as carbon dioxide and urea.
Five Examples of Facilitated Diffusion
1. Glucose Transport: Glucose is an important molecule that provides energy to cells. It is transported across the cell membrane via facilitated diffusion, using the glucose transporter (GLUT1) protein.
2. Chloride Ion Transport: Chloride ions are important for maintaining the correct pH inside a cell. They are transported across the cell membrane via facilitated diffusion, using a chloride ion channel.
3. Sodium/Potassium Pump: The sodium/potassium pump is an important protein that helps regulate the levels of sodium and potassium ions inside a cell. It is transported across the cell membrane via facilitated diffusion, using a sodium/potassium pump protein.
4. Amino Acid Transport: Amino acids are used for numerous purposes in the body, including building proteins. They are transported across the cell membrane via facilitated diffusion, using various amino acid transporter proteins.
5. Thyroid Hormone Transport: Thyroid hormones are important for the regulation of metabolism. They are transported across the cell membrane via facilitated diffusion, using a thyroid hormone transporter protein.