Question

Give an example of antiport.

Answer 1

Hint: The movement of particles or molecules across the cell membrane is known as cell transport. The substances can either move in or out of the cell. Moving into the cell is known as endocytosis and moving out of the cell is known as exocytosis.

Complete answer:
During the transportation of substances across the cell membrane, the molecules have to cross the phospholipid bilayer and for that, the molecule has to be lipid-soluble. If it is water soluble, it cannot cross the lipid bilayer on its own. There are basically three types of transports i.e., Active transport, Passive transport and facilitated transport.
Active transport is the type of transport in which substances move from a lower concentration to a higher concentration against the concentration gradient. This requires the use of an ATP so therefore we can say that it is an energy driven process.
Passive transport does not require any use of energy and the substances pass along the concentration gradient i.e. from a higher concentration to a lower concentration.
Facilitative transport includes the use of facilitators like channel proteins that help water soluble molecules to cross the lipid bilayer.
The active transport is mainly of two types i.e., Antiport and symport system.
Antiport system is a type of active transport that includes two species of solutes or ions that are pumped in opposite directions across the cell membrane. One of these two species is allowed to flow from high concentration to low. This produces enough energy to carry the transport of outer solute from low concentration to a high concentration region. An example of this system is the sodium-calcium antiporter or exchanger. This allows three sodium ions into the cells for the transport of one calcium ion.
Symport system is another type of active transport that includes a mechanism of transport across the cell membrane that allows two different molecules to move in the same direction. Its example includes a sodium-glucose symporter system.

Note:
A uniport is the transport of only one molecule, without coupling to the transport of another molecule or ion. An example of a uniporter is the glucose transporter (GLUT) found in erythrocytes. This allows glucose to enter the cell via facilitated diffusion and it does so at approximately 50,000 times the rate that it would via simple diffusion.