The external coverings of diatoms are made up of (cellulose, silica, chitin) , while slime molds have cell walls containing (cellulose, silica, chitin). Diatoms are (chemoautotrophs, chemoheterotrophs, photoautotrophs) because they make food through photosynthesis, while slime molds are (autotrophs, heterotrophs, phototrophs) because they eat decaying plant matter.