Antiport carrier proteins
a. allow 2 molecules to be transported in the same direction at the same time
b. allow 2 molecules to be transported in opposite direction at the same time
c. allow 1 molecules to be transported
d. allow 6 molecules to be transported in opposite directions at the same time

Option (b).

Explanation:

Carrier proteins allow the movement of the particles inside and outside the cells. Three types of porter are uniport, symport and antiport. These porters transport molecules in the different directions.

The antiporters transport two molecules at a time. These two molecules are transported in the opposite directions at the same time. The one molecule will move inside the cell and the other molecule will move outside the cell.

Thus, the correct answer is option (c).

velocity and height

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.