Transport in plants occurs over long distances through the vascular system or within cells. Materials move in and out of cells by diffusion, facilitated diffusion, or active transport. Diffusion is a passive, slow movement along a concentration gradient without energy expenditure. Facilitated diffusion uses helper proteins like porins and aquaporins to selectively transport hydrophilic substances without expending energy. Active transport moves substances against a concentration gradient faster than passive transport by utilizing ATP as an energy source.