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If cells are alive, do they eat? Cells are the fundamental units of life and exhibit the same properties as multicellular organisms. Individual cells reproduce and maintain a fairly constant internal environment. They also take in energy and nutrients and excrete waste. Cells in a multicellular organism generally transport individual molecules across the cellular membrane to accomplish the equivalent of eating and excretion. However single celled organisms may not encounter food in the form of individual molecules. Therefore cells have evolved mechanisms for moving objects larger than individual molecules across cellular membranes. The mechanisms are endocytosis and exocytosis for moving material into and out of cells, respectively.