What type of transport requires energy to move substances across a membrane?

Active transport is the process that requires energy to move substances across a cell membrane. This type of transport is essential for maintaining the proper concentrations of ions and molecules inside and outside of cells, allowing for various cellular functions to occur.

In active transport, substances are moved against their concentration gradient, meaning that materials are transported from an area of lower concentration to an area of higher concentration. This is contrary to passive transport methods, such as simple diffusion and facilitated diffusion, which do not require energy and occur along the concentration gradient, allowing molecules to move freely from regions of higher concentration to regions of lower concentration.

The energy used in active transport usually comes from ATP (adenosine triphosphate), which is the primary energy currency of the cell. Examples of active transport include the sodium-potassium pump, which helps maintain the electrochemical gradient across the cell membrane by actively moving sodium ions out of the cell and potassium ions into the cell. This active process is crucial for cell signaling, nutrient uptake, and waste removal.