Final answer:
Primary active transport directly uses ATP to move ions across a membrane, creating an electrochemical gradient. Secondary active transport relies on this gradient to transport substances without directly using ATP. Despite this indirect reliance on ATP, secondary active transport still requires energy and is thus considered active.
Step-by-step explanation:
When comparing primary active transport and secondary active transport, there are key differences to note. Primary active transport is a process that moves ions across a membrane, creating a charge difference, and is directly dependent on ATP for energy. In contrast, secondary active transport does not use ATP directly. Instead, it relies on the electrochemical gradient created by primary active transport to move materials. This gradient serves as the energy source that drives the transport of other substances like amino acids and glucose into the cell through membrane channels.
It is critical to understand that while secondary active transport does not use ATP directly, it is still considered active transport because it is energized by the gradient established by primary active transport, which does require ATP. Furthermore, ATP itself can be formed through secondary active transport in structures like the mitochondrion, using a hydrogen ion gradient. The maintenance of the membrane potential, driven by the sodium-potassium pump, is essential for vital bodily functions and consumes a significant portion of the body's energy.