Question

Which of the following is a type of co-transport?
A. Antiport
B. Symport
C. Both A and B
D. Uniport

Answer 1

Hint: Cotransporters are proteins present on the membrane of a cell that plays an important role in the exchange of molecules. It acts as a vehicle that drives molecules in and out of the cell.

Complete step by step answer: Cotransport is a process of movement of two substances at the same time. It is a means of secondary active transport that requires energy. Symport is a type of cotransport. Here, substances move at the same time and in the same direction. An example of a symport process is the transport of amino acids across the intestinal lining in the human gut. Whereas, antiport is also the type of cotransport where two substances flow at the same time but in different directions. An example of an antiport process is the transport of Calcium ions out of cardiac muscle cells.
Cotransporters are protein pumps used to export or import small molecules. The electrochemical gradient of the cotransporter is due to the movement of sodium and hydrogen ions. Cotransporters are also capable of moving solutes either up or down the gradient at rates of thousand to ten thousands molecules per second.

Additional information: Cotransporters are a subcategory of membrane transport proteins that couple the favourable movement of one molecule with its concentration gradient and unfavourable movement of another molecule against its concentration gradient.

Note: ATP is not directly involved in the functioning of a cotransporter, but cotransporter is considered a means of active transport. Though molecules move against their gradient, therefore it does not directly require any chemical source of energy such as ATP.