Question

When transport proteins simultaneously move two molecules across a membrane in the same direction, the process is called-
A. Uniport
B. Antiport
C. Symport
D. Diffusive port

Answer 1

Hint: A transport protein is also referred to as a transporter or carrier protein. Carrier protein is such a protein which involves in the transport of ions small molecules, or macromolecules, such as another protein, across a plasma membrane. As there are different types of ions and molecules found, so there is a different process of transport and different type of transport protein are also found.

Complete answer:
Transport proteins serve the function of moving of various ions, molecules, and macromolecules from one cell to another. This transport of substance can be occurred by facilitated diffusion i.e. passive transport or active transport. This mechanism of transport is called carrier-mediated transport.
In the case of active transport, some specific carrier proteins or pumps are present to facilitate movement. There are three types of these proteins or transporters found, which are uniporters, symporters, and antiporters. In some cases, there is some transporter or carrier protein present which allows two molecules to move at the same time. This type of transport is called cotransport. There are two types of cotransport recognized, one is symport and the other is antiport.
In the process of antiport, there are two parallel passages in the plasma membrane. Through these passages, two molecules moved in opposite directions of each other. An antiporter protein carries two different ions or molecules but in opposite directions.
In the uniport transport, a uniporter carries one specific ion or molecule. In this type of transport, there is only one passage through which a molecule across the membrane. In the uniport movement, molecules move independently of other molecules and ions.
A diffusive port is one type of passive transport through this process transport of some small substance solutes takes place in the plasma membrane. It depends on the cell membrane permeability. Various small, uncharged substances such as oxygen and carbon dioxide and some hydrophobic molecules such as lipids are passed through this process.
In another process of cotransport, which is known as symport, there are also two parallel passages, and using this passage both the molecules travel in the same direction simultaneously. A symport carrier protein carries two different ions or molecules, both in the same direction.

Therefore, the correct option is option C.

Note:
In living organisms, various ions, molecules, and macromolecules are transported always from one cell to another. This transport takes place with the help of transport or carrier proteins. According to the nature of transport, there are three main methods of transport. The transport of an independent molecule is called uniport. When two molecules move in the opposite direction is called antiport and when two molecules move across the membrane simultaneously in the same direction is called symport.