Most organisms in the Protista kingdom have a mitochondrion. Mitochondria are the primary source of energy in the cell, as it is here that it converts ATP (adenosine triphosphate) into energy. Mitochondria are made up of protein and often contain multiple layers. Additionally, mitochondria are often the location of gene-rich DNA. However, not all organisms in the Protista kingdom have a mitochondria; for example, organisms in the Archaezoa group do not have one. In many organisms in the Protista kingdom, the mitochondria is often the only significant interior organ.
Several organisms in the Protista kingdom have flagella, which is like a tail on the exterior of the cell and allows for the cell to move. Flagellum are made up of three parts: the filament, the structure that comes directly from the cell's interior; a basal body, which controls the movement; and a hook, which connects the filament and the basal body. Protists that have flagella include the dinoflagellate, which are famous for causing the phenomena known as "red tide."
Some organisms in the Protista kingdom have a pseudopod (Greek for "false foot"). A pseudopod is filament on the exterior of the cell that it allows it to extend around its food, and then subsequently pulls the rest of the cell around it. The pseudopod can be used to either catch food or to slowly move the organism. The most well-known example of an organism with a pseudopod is the amoeba, which is in the Rhizopod group.
A third type of movement for Protista is found in the cellular component known as cilia. Cilia are tiny hairlike follicles that extend from the cell's membrane, and which beat back and forth. Much like the pseudopod, a Protista with cilia will move itself directly over its food. The cilia themselves are made up of 10 pairs of microtubulues. Examples of Protista with cilia include the paramecium and the Stentor.