Cilia are tiny, hairlike filaments that protrude from a paramecium's body. The organism uses them like oars to move it in the direction it wants to go. Unlike carnivorous animals, paramecia do not stalk their prey. Instead, they move through water until they find food. Depending upon the direction its cilia beat, the paramecium can go forward, backward or sideways in search of nutrition.
Once it encounters a food source, a paramecium uses cilia to sweep it into its oral groove. This is not a mouth leading to a digestive track, as animals and humans have, but it resembles a mouth because it is a cavity where the food enters. The oral groove ends in the gullet, which serves as a temporary storage facility.
Once enough food accumulates in the gullet, a paramecium's cell begins to change shape. Protrusions form as cytoplasm streams toward the food particle. These protrusions grow around the particles, engulfing them and pinching off the end of the gullet in a process called phagocytosis. The resulting structure is a food vacuole, which is like a package that holds the food until it can be digested.
Although the food vacuole is completely contained inside the paramecium, the food has not been digested. It is like food that is still in the pantry. For the paramecium to use the food, it must first digest it. Organelles called lysosomes perform this function by fusing with the vacuoles and emptying digestive enzymes inside. This breaks down the food into small pieces, which can then pass through the pores of the vacuole membrane as it travels through the cell, supplying food to the paramecium.