Active transport is the biological process by which molecules or ions move across a cell membrane against their concentration gradient (i.e., from an area of lower concentration to an area of higher concentration). Because this movement opposes the natural direction of diffusion, it requires energy (usually in the form of adenosine triphosphate, ATP) and the assistance of specific carrier proteins or pumps .
Active transport is the biological process by which molecules or ions move across a cell membrane against their concentration gradient (i.e., from an area of lower concentration to an area of higher concentration). Because this movement opposes the natural direction of diffusion, it requires energy (usually in the form of adenosine triphosphate, ATP) and the assistance of specific carrier proteins or pumps .
