What type of transport requires cellular energy (ATP)?

Active transport is a process that requires cellular energy, primarily in the form of ATP, to move substances across a cell membrane against their concentration gradient. This means that substances are transported from an area of lower concentration to an area of higher concentration, which is not a spontaneous process and therefore requires energy input.

In contrast, facilitated diffusion, osmosis, and diffusion all occur passively. These processes do not require energy because they utilize existing concentration gradients to move substances across the membrane. For example, facilitated diffusion involves specific proteins aiding the movement of molecules down their concentration gradient, whereas osmosis specifically refers to the movement of water across a semi-permeable membrane. Diffusion involves the spread of particles from an area of higher concentration to an area of lower concentration until equilibrium is reached. Active transport is crucial for various biological processes, including nutrient uptake and the removal of waste products from cells, highlighting its importance in maintaining cellular function.