A cell needs to take up Na+ ions. The concentration of Na+ outside the cell is 200 ppm, and inside the cell it is 350 ppm. Which type of transport will the cell use?

To determine which type of transport the cell will use to take up Na+ ions, we need to compare the concentrations of Na+ ions inside and outside the cell.

The concentration of Na+ ions outside the cell is 200 ppm (parts per million), while inside the cell it is 350 ppm. Based on this information, we can see that the concentration of Na+ ions is higher inside the cell compared to the outside.

In order to move ions against their concentration gradient (from an area of lower concentration to higher concentration), the cell would require active transport. Active transport is a process that requires energy to move substances across a cell membrane.

Therefore, the cell in this scenario will likely use active transport to take up Na+ ions.