Which process turns food into energy in any cell? a) photosynthesis
or b) cellular respiration

Cellular respiration is the process to divert food into energy. 

Metabolism is the chemical reactions that take place inside a living organism. The reaction occurs in the cells.  Digestion can be the best association to metabolism. The metabolic system recognizes which substances can be nutritious or poisonous. In order to complete this process, water is needed.  The chemicals are dissolved in water and transported. Without water, no reaction can take place.

Metabolism is considered as the set of life-sustaining chemical reactions within the living organism’s body cells.