Answer:
19. Active transport is a process by which cells move molecules or ions across their membranes against a concentration gradient, using energy from ATP.
11. The type of organic molecule needed for active transport is ATP (adenosine triphosphate), which provides the energy required to move molecules or ions against a concentration gradient.
12. Endocytosis is a process by which cells take in molecules or particles from the outside environment, by engulfing them in a vesicle. Exocytosis is the opposite process, by which cells release molecules or particles from inside the cell to the outside environment.
13. The main difference between diffusion and active transport is that diffusion is a passive process that does not require energy, whereas active transport requires energy from ATP to move molecules or ions against a concentration gradient.
14. Once materials diffuse into a cell, they can enter the cell's metabolic pathways and be used for various cellular processes, such as energy production or the synthesis of new molecules. Alternatively, they can be stored inside the cell for later use.