Which of the following is the correct sequence of events that causes auxin to move in a polar direction in a plant stem?
A) The ionized auxin is transported into the cell by efflux carriers, the auxin gains a proton in the basic cytosol, and the nonionized auxin passively diffuses out of the base of the cell.
B) Auxin picks up a proton in the basic cell wall space, the nonionized auxin passively diffuses across the cell membrane into the cell, the auxin loses a proton in the more acidic cytosol, the ionized auxin is transported out of the cell by an efflux carrier located only at the base of the cell, and the proton pumps in the cell membrane acidify the cell wall space.
C) Auxin passively diffuses into the cell as an anion, auxin stimulates proton pumps in the cell membrane to acidify the cytosol, the auxin picks up a proton to become uncharged, and the nonionized auxin is actively transported out of the cell by efflux carriers.
D) Proton pumps in the cell membrane acidify the cell wall space, auxin picks up a proton in the acidic cell wall space, the nonionized auxin passively diffuses across the cell membrane into the cell, the auxin loses a proton in the more basic cytosol, and the ionized auxin is transported out of the cell by an efflux carrier located only at the base of the cell.
E) Auxin moves down its concentration gradient from the tip of the plant where it is made to the base where it is used, passively entering and exiting each cell along the way.

Question

Quizplus · Accepted Answer

The correct sequence involves proton pumps acidifying the cell wall space, which allows auxin to pick up a proton and become nonionized, enabling it to diffuse into the cell. Inside the cell, auxin loses the proton in the basic cytosol and becomes ionized, which is then actively transported out by efflux carriers located at the base of the cell. This process ensures the polar movement of auxin down the plant stem.

Which of the Following Is the Correct Sequence of Events