Every healthy organism stores some of its biochemical energy in reserves (e.g. adipose tissue, glycogen), but much of an organism's biochemical energy is bound in ways that aren't normally accessible to it (e.g. protein in muscles or vital organs).

The latter quantity has some thermodynamic implications. For example, the inaccessible energy can be transferred to a predator if the organism is eaten, and a fetus's inaccessible energy must be obtained from its mother.

To research these concepts, I'm looking for a term for energy that's accessible by the organism and a term for energy that's not accessible by the organism.

I've searched the web (and StackExchange specifically) for a variety of terms, (e.g. "expendable", "reserved", "essential", "innate", etc.) but none of them produced relevant results.