Dynamic reserve, in the context of the dynamic energy budget theory, refers to the set of metabolites (mostly polymers and lipids) that an organism can use for metabolic purposes.
Reserve has an implied turnover, because it is synthesized from food (or other substrates in the environment) and used by metabolic processes occurring in cells.
A freshly laid egg consists almost exclusively of reserve, and hardly respires.
Reserves are synthesized from environmental substrates (food) for use by the metabolism for the purpose of somatic maintenance (including protein turnover, maintenance of concentration gradients across membranes, activity and other types of work), growth (increase of structural mass), maturity maintenance (installation of regulation systems, preparation for reproduction, maintenance of defense systems, such as the immune system), maturation (increase of the state of maturity) and reproduction.
Polymers (carbohydrates, proteins, ribosomal RNA) and lipids form the main bulk of reserves and of structure.