Question

If the concentration of phosphate in the cytosol is 2.0 mM and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol?

a) passive transport
b) diffusion
c) active transport
d) osmosis
e) facilitated diffusion

Answer 1

It must be answer c. As the concentration of phosphate is much higher in the cell than outside, there can't be any passive transport or diffusion, so the cell has to invest energy to higher the concentration inside.