Question

The image shown below is the movement of molecule A across the plasma membrane by facilitated diffusion. The type of facilitated diffusion shown in the image is

• A. symport
• B. uniport
• C. antiport
• D. simple diffusion

Answer 1

The correct option is B uniport

Molecule A is moving across the membrane with the help of a carrier protein.
There are three types of facilitated diffusion: Uniport, Symport and Antiport.
In uniport type of movement, carrier proteins transport a single molecule across the membrane.
In symport, the carrier proteins transport two molecules across the membrane in the same direction. In antiport, the carrier proteins transport two molecules across the membrane in the opposite direction. Unlike uniport, in symport and antiport, the movement of two molecules is dependent on each other.
In simple diffusion, molecules move across the membrane without the help of proteins.