Here's why:
* ATP is the universal energy currency of cells: Cells use ATP to power a wide range of activities, including muscle contraction, protein synthesis, and active transport.
* Phagocytosis is an active process: It requires energy to:
* Move the cell membrane: The cell membrane needs to engulf the target particle.
* Transport the particle inside the cell: The particle is enclosed in a phagosome, which requires energy for its formation and movement.
* Process the particle: Once inside the cell, the phagosome fuses with lysosomes, which contain enzymes to break down the engulfed material. This enzymatic activity requires ATP.
While other molecules contribute to the process, ATP is the direct source of energy for the key steps of phagocytosis.
