In this case, in active transport, we see that we actually move the molecule against the electrochemical gradient. So in some cases, we need to move ions or molecules against their electrochemical gradient. And one example is the neuron cell that basically uses active transport to create an electrochemical gradient to allow the propagation of our action potential, our electrical signal. And we'll discuss that in much greater detail when we get to that subject. So basically, this type of active transport requires not only energy, it also requires a specialized type of integral protein. And two types of active transport exist.