Cellular transport refers to the movement of substances into and out of cells. This process is essential for maintaining homeostasis, allowing cells to obtain nutrients and expel waste. There are two main types of transport: passive and active. Passive transport does not require energy and includes processes like diffusion and osmosis, where molecules move from areas of high concentration to low concentration. Active transport, on the other hand, requires energy to move substances against their concentration gradient. This is often facilitated by proteins in the cell membrane, such as transport proteins or pumps. Together, these mechanisms ensure that cells function properly and respond to their environment.