Fundamental material composing all living things. Protoplasm, which exists in all plants and animals in the small units called cells, is mainly (85-90 percent) water and also contains
proteins, fatty substances and inorganic salts. It is always enclosed by a thin surface membrane that controls the passage of materials into and out of the cell. It displays the general properties associated with life-the capacity to respond to stimuli and the ability to perform the essential physiological functions.