What process uses ATP to move substances against their concentration gradient?

The process that uses ATP to move substances against their concentration gradient is known as primary active transport. In this mechanism, energy derived from ATP hydrolysis is utilized to transport ions or molecules across a membrane from areas of lower concentration to areas of higher concentration, which is contrary to the natural direction of diffusion.

This process is crucial for maintaining cellular homeostasis and involves specific membrane proteins called pumps. A classic example is the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into it. This action is essential for various cellular functions, including nerve impulse transmission and muscle contraction.

In contrast, simple diffusion and facilitated diffusion are passive transport mechanisms, meaning they do not require energy. These processes allow substances to move along their concentration gradients, from areas of higher concentration to lower concentration. Secondary active transport also does not directly use ATP; instead, it relies on the electrochemical gradients created by primary active transport to move other substances against their gradients.