What are 3 chemicals used in digestion and what do they do?

Food provides molecules that serve as fuel and building material for all organisms. plants undergo photosynthesis and make their own food. other organisms, like us and the horse seen above, are consumers and eat food. how do all organisms use food as fuel? be sure to include the name of the process in your answer. me.

Would really appreciate it, i have an idea but not completely sure

What field of science did harry hess study?