The Golgi complex, or Golgi apparatus, is a membranous structure composed of stacks of thin sacs. Newly made proteins move from the endoplasmic reticulum to the Golgi complex, where they are stored for later secretion. Vacuoles drift through the cytoplasm and usually carry food molecules in solution. Vacuoles also regulate the water content of certain one-celled animals. When an amoeba, for example, absorbs too much water, it forms a contractile vacuole against the membrane.
Lysosomes are structures somewhat similar in appearance to vacuoles but denser.
They appear to have a digestive function. Each lysosome is filled with digestive enzymes and encased in a membrane. Lysosomes are believed to break down food substances brought into the cell by pinocytosis. It has been suggested that the Golgi complex plays a part in the formation of lysosomes. Plastids in the cytoplasm of plants and one-celled animals synthesize and store food and other materials, such as starch or a working chemical.