Posted: February 1st, 2023
The plasma membrane of the cell is made of a phospholipid bilayer, and it does not allow substances to pass through it quickly. The plasma membrane is hydrophobic, so it does not allow the polar (hydrophilic) molecules to enter the cell. Some of the non-polar (hydrophobic) molecules also require mediators and carriers to cross the membrane. The mediators of facilitated diffusion are carrier and channel proteins. Channer pores are found in the membrane that supports the transportation of molecules in the case of the channel protein. Charged ions can be carried inside the plasma membrane with the help of a channel protein complex. Carrier proteins present on the biological membranes bind with the molecules that need to be transported. These molecules undergo some conformational changes that facilitate the movement of molecules into the cytoplasm. Enzymes, the biocatalysts, move across membranes with the help of facilitated diffusion.
Channel Protein and carrier protein
The channel proteins form the channel in the plasma membrane; these are also known as integral protein. They support the transportation of molecules across cell membranes through the channel present on biological membranes. Some of the channels are selective, which allows only a few substances to pass through them. Channel proteins have hydrophilic domains that are exposed to the intracellular and extracellular matrix. The hydrophilic core of the proteins provides the hydrate opening through the plasma membrane layer. Carrier protein is a collective group of proteins that helps in carrying out facilitated diffusion. The binding sites of the carrier proteins are very selective, and therefore, these proteins make the plasma membrane selectively permeable. The substances bind to these proteins, and their shape undergoes a conformational change.
Factors affecting facilitated diffusion
The concentration gradient is an important factor in carrying out facilitated diffusion because this process occurs from a highly concentrated region to a region of low concentration. As the temperature increases, the rate of facilitated diffusion also increases because the rate of reaction is increased. The diffusion process is selective because a few molecules are not allowed to pass the membrane due to the presence of carrier proteins.
Some examples of Facilitated diffusion
The transportation of glucose and the amino acid molecules is brought about with the help of facilitated diffusion. Amino acid and glucose molecules both require carrier proteins. The transportation of gases in the muscles and blood also occurs with the assistance of facilitated diffusion. Some ions like calcium and sodium are transported in the transmembrane by facilitated diffusion
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