Every healthy organism stores some energy in reserves (e.g. adipose tissue), but much of its energy is stored in essential structures (e.g. heart muscle).

The distinction between these two kinds of energy deposits is useful for modeling ecology, Are there any formal terms for them--especially the latter?

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

P.S.: I understand that applying this distinction could be difficult. For example, skeletal muscle contains both essential/innate energy from its protein and expendable/reserved energy from its glycogen.