What is the primary difference between active and passive transport?

The distinction between active and passive transport is fundamentally rooted in the requirement of energy. Active transport necessitates the use of cellular energy, typically in the form of ATP, to move molecules against their concentration gradient, meaning from an area of lower concentration to one of higher concentration. This process enables cells to accumulate substances that they might need for specific functions, even when those substances are less concentrated outside the cell.

In contrast, passive transport does not require any additional energy expenditure; it relies on the natural tendency of molecules to move from regions of higher concentration to lower concentration. This movement occurs through processes like diffusion or facilitated diffusion until equilibrium is reached.

Understanding this difference is crucial, as it highlights how cells can regulate their internal environments and maintain homeostasis despite varying external conditions. While energy consumption is a key differentiating factor, it's important to note that both types of transport are vital for cellular function and overall organismal health.