Question

Suppose the pH in the cell walls of an apical meristem became highly basic ( > pH 7), but traffic through PIN proteins in the membrane remained normal. Where would you expect most auxin molecules to be concentrated—in the cell wall or cytoplasm? Would the auxin molecules be in the charged or uncharged form?

a)cell wall; uncharged form

b)cell wall; charged form

c)cytoplasm; charged form

d)cytoplasm; uncharged form

This is all the information I was provided.

Answer 1

The auxin molecule will be in (b) Cell Wall- charged from.

After entering in a cell through cell wall, auxin cannot leave the cell by crossing the cell lipid bilayer. So, an active transport system in the plasma membrane is required for auxin to leave the cell. These are called transport proteins. Two protein families namely The PIN proteins and ABCB (PGP proteins) transporters function as "auxin efflux carriers". These transport proteins transport the anionic form of auxin out of the cell.

While the PGP auxin efflux carriers are evenly distributed, the PIN proteins normally maintain polar (i.e. charged) localisation on the plasma membrane. This PIN-generated flow is called auxin polar transport.