Facilitated Diffusion Facilitated diffusion is the passive movement of molecules along the concentration gradient. It is a selective process, i.e., the membrane allows only selective molecules and ions to pass through it. It, however, prevents other molecules from passing through the membrane. The electric charge and pH helps in the diffusion across the membrane. In living systems, the lipid based membrane creates compartments which allow the transport of a selective concentration of water-soluble substances. The ions, small molecules, proteins, and other solutes have different concentration across the membranes. Hydrophilic, polar or charged molecules cannot cross the membrane. Recommended Video:Factors Affecting Facilitated DiffusionBrownian motion is the force behind the diffusion of fluids. The main factors affecting the process of facilitated diffusion are:
Importance of Facilitated DiffusionNot every molecule can cross the cell membranes. The molecules should be small and non-polar to traverse the membrane. For eg., glucose is a large molecule that cannot diffuse across the cell membrane. Ions like sodium, potassium, and calcium are charged and are repelled by the cell membrane. Amino acids and nucleic acids are polar and too large to cross the cell membrane. Also, the water movement across the membrane in bulk is difficult at times. To facilitate these transfer of substances across the membrane, certain integral membrane proteins or the transmembrane proteins are required. They are channel proteins and carrier proteins. Transmembrane ProteinsTransmembrane proteins are the proteins present in the cell membrane that facilitate the movement of certain molecules across the membrane. There are certain channel proteins and carrier proteins that accelerate the transport process.
There are certain transmembrane proteins that help in the movement of solutes and ions. Examples of Facilitated DiffusionFollowing are the important examples of facilitated diffusion: Glucose TransporterThese facilitate the transport of glucose across the plasma membrane. These are present in the plasma membrane that binds the glucose molecules and transports them across the lipid bilayer. The glucose transporters are of two types- sodium-glucose cotransporters which are present in the small intestine and renal tubules and are responsible for the glucose transport against the concentration gradient, and the facilitative glucose transporters which are responsible for the bidirectional movement of glucose molecules across the plasma membrane. AquaporinsThese proteins facilitate the transport of water across the lipid bilayer. If the proteins forming aquaporins are mutated, it might result in diseases such as diabetes insipidus. Ion ChannelsThese are transmembrane proteins that allow the selective transport of ions and solutes across the plasma membrane. These ionic pumps maintain the concentration of the extracellular fluid different from that of the cytosol. When an excess of sodium ions are present in the extracellular region and excess of potassium ions are present inside the cell, a resting potential is obtained. With a small voltage change, the sodium ion channels open and the sodium ions rapidly enter into the cell. The potassium ion channels also open and the ions move out of the cell. For more information on Facilitated Diffusion, its importance, examples and factors affecting facilitated diffusion, keep visiting BYJU’S Biology website or download the BYJU’S app for further reference. Related LinksWhat is the term for the movement of molecules from an area of greater concentration to an area of lesser concentration hint no energy required?Diffusion is the movement of particles from areas of higher concentration to areas of lower concentration. It is a natural, random process. This means that it does not require extra energy input.
What is the movement of molecules from an area of greater concentration to an area of lesser concentration?Diffusion is defined as the net movement of molecules from an area of greater concentration to an area of lesser concentration. The molecules in a gas, a liquid or a solid are in constant motion due to their kinetic energy.
What is it called when molecules move across the membrane from an area of high concentration to an area of low concentration through a carrier protein?An example of passive transport is diffusion, the movement of molecules from an area of high concentration to an area of low concentration. Carrier proteins and channel proteins are involved in facilitated diffusion.
|