Four different types of protists exist, and each type obtains energy from food differently. Depending on the category, sunlight, chemicals, food from outside the body and creating digestive enzymes are all ways that these tiny organisms ingest the nutrients that they need.
Heterotrophs are organisms that cannot produce their own food. Heterotrophic protists are also known as detritivores, which means that they feed on the remains of deceased animal and plant material. The food that they ingest combines with digestive enzymes to release the nutrients they require into their systems.
Another type of heterotrophic protist sends its digestive enzymes into its environment. After the enzymes have interacted with the plant and animal matter around it, this type of protist absorbs the nutrients through its membrane. This is similar to the first type of heterotrophic protist, but this type lacks a mouth through which to draw nutrients.
Autotrophs can produce their own food and nutrients internally. One type of autotrophic protist uses the process of photosynthesis. Sunlight provides the energy for chemical reactions inside the protist, and glucose emerges to power the organism.
The other type of autotrophic protist uses chemical reactions inside its body to produce nutrients, but these chemical reactions can run even in the absence of light.