8. An experiment is designed to study the mechanism of sucrose uptake by plant cells. Cells are immersed in a sucrose solution and the pH of the solution is monitored. Samples of the cells are taken at intervals and their sucrose concentration is measured. Their sucrose uptake correlates with a rise in the solution's pH. This rise is proportional to the starting concentration of sucrose in the solution. A metabolic poison that blocks the ability of cells to regenerate ATP is found to inhibit the pH changes in the solution. Propose a hypothesis accounting for these results. Suggest an experiment to test it.