Heterotrophic organisms are contrasted
with autotrophic life forms in that their carbon needs derive from organic
nutrients which they take up from the growth environment. These organic
nutrients are also used as the source of reducing equivalents for reductive
biosyntheses and, in addition, their oxidation provides the free energy
needed to support a chemiosmotic mechanism which powers ATP synthesis.
Animals are heterotrophs, and most microorganisms are hetertrophs.