Concentrations of calcium ions (Ca2+) are generally very low inside cells. If Ca2+ is present in high concentrations outside the cell, which of the following transport mechanisms would be the most appropriate and efficient for transporting Ca2+ into the cell?
a carrier protein
Under the same conditions, what type of transport mechanism would be appropriate to move Ca2+ out of the cell?
primary active transport (a "pump")
Given the normal Ca2+ gradient initially described above, suppose that another molecule "X" can be transported into the cells by secondary active transport, using the gradient of calcium ions for energy. Given that secondary active transport is being used to transport "X", what must the concentration gradient of "X" look like? "X" is low inside the cell, and high outside