Describe the different forms of active transport across a biological membrane

Active transport is the movement of solutes, either ions or molecules, across a membrane up their concentration gradient (from low to high concentrations). The process requires a carrier protein which is embedded in the membrane. Primary active transport refers to that being driven by the energy currency molecule ATP. The protein carrier will use the energy stored in the ATP molecule to actively transport the solute across the membrane. Secondary active transport refers to when other forms of energy are used to actively transport the solute across. An example is the proton (H⁺) gradient, where the energy released from the protons passively diffusing down their concentration gradient (through the same carrier protein) is used.