1. You are testing the rate of glucose transport into vesicles using the Na + gl
ID: 37824 • Letter: 1
Question
1. You are testing the rate of glucose transport into vesicles using the Na + glucose pump. A. in experiment 1, you employ liposomes that have the pump in the same orientation as that found in the plasma membrane in epithelial cells. These liposomes contain glucose but no Na+ ions. You then transfer the liposomes to a series of tubes with solutions containing the same glucose concentration as that inside the vesicle and 0, 1, 2, 3, or 10 mM Na+. You measure the initial rates of glucose transport and plot you results: A. Why do the initial rates of glucose transport into the liposome reach a plateau as the concentration of Na+ increases?Explanation / Answer
The transport of Na+ and glucose into the cell is an example of Symport. For every two sodium ions transported into the cell, glucose is also transported in the same direction. The concentration gradient of sodium is used to transport glucose into the cell, against the concentration gradient. That is, though the concentration of glucose in the cells is higher than the external compartment, it is transported into the cell.
In the given experiment, initially there are no Sodium ions (Na+) inside the cell. There is a concentration gradient, and so, sodium ions are transported into the cell. Along with the sodium ions, glucose is also transported. As the cell’s external and internal compartments reaches equilibrium with respect to Na+ ions, there is no net movement of the ions into the cell. Therefore, symport of glucose is stopped.
With increased concentrations of Na+ ions, the rate of transport of the ions also increases. Therefore, the concentration gradient across the membrane decreases at a faster pace, the cell reaches equilibrium quickly with high sodium ion concentrations. This gives the plateau in the graph.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.