Question

the illustration shows the active transport of hydrogen ions through a membrane protein. which of the following best predicts the effect of not having atp available to supply energy to this process? (a) h+ ions will stop moving through the protein. (b) h+ ions will move in the other direction through the protein. (c) h+ ions will continue to move through the protein in the original direction but at a slower rate. (d) h+ ions will begin to move through the phospholipid portion of the membrane in the original direction.

Explanation:

Active transport requires ATP to move substances against their concentration gradient. Without ATP, the energy - dependent process of moving \(H^+\) ions through the membrane protein (which is an active transport mechanism as indicated by the use of ATP in the illustration) will stop. Option B is incorrect because there is no indication that without ATP, \(H^+\) ions would reverse direction. Option C is wrong since active transport (not a facilitated diffusion - like process that could have a slower rate without energy if it were a passive process with a carrier) depends on ATP for the movement against the gradient. Option D is incorrect because \(H^+\) ions are charged and cannot easily pass through the phospholipid bilayer (which is non - polar in the interior) without a protein channel or pump, and the original process is through a protein, not the phospholipid portion.

Answer:

A. \(H^+\) ions will stop moving through the protein.