Nitrogen waste is produced when proteins are digested. Proteins are composed of amino acids. The nitrogen-containing portion of the molecule is converted to ammonia. This is a toxic material, and the cell must rid itself of it. Ammonia, the nitrogen waste, leaves protozoans by diffusion.
Aerobic respiration produces carbon dioxide as a waste product.
Carbon dioxide waste leaves protozoans by diffusion to the water surrounding the protozoan. Aerobic respiration is possible only if oxygen is present in protozoan cells. Oxygen enters protozoans by diffusion from the water surrounding the protozoan. Protozoans are a diverse group of organisms. Protozoans have several special features.