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 Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

purposes. These chemical compounds can have active metabolic functions, however. They are not just "set apart for later use." Reserve differs from structure in the first place by its dynamics. 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. The turnover of structure depends on the maintenance of an organism. Maintenance is not required for reserve. A freshly laid egg consists almost exclusively of reserve, and hardly respires. The chemical compounds in the reserve have the same turnover, while that in the structure can have a different turnover, and so it depends on the compound.

Functionality

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 Growth may refer to: Biology * Auxology, the study of all aspects of human physical growth * Bacterial growth * Cell growth * Growth hormone, a peptide hormone that stimulates growth * Human development (biology) * Plant growth * Secondary growth ...

(increase of structural mass), maturity maintenance (installation of regulation systems, preparation for reproduction, maintenance of defense systems, such as the immune system),

maturation Maturation is the process of becoming mature; the emergence of individual and behavioral characteristics through growth processes over time. Maturation may refer to: Science * Developmental psychology * Foetal development * Maturity (geology), ...

(increase of the state of maturity) and

reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...

. This organizational position of reserve creates a rather constant internal chemical environment, with only an indirect coupling with the extra-organismal environment. Reserves as well as structure are taken to be generalised compounds, i.e. mixtures of a large number of compounds, which do not change in composition. The latter requirement is called the strong homeostasis assumption. Polymers ( carbohydrates, proteins, ribosomal RNA) and lipids form the main bulk of reserves and of structure. Some reasons for including reserve are to give an explanation for (from ): # the metabolic memory; changes in food (substrate) availability affect production (growth or reproduction) with some delay. Growth continues for some time during

starvation Starvation is a severe deficiency in caloric energy intake, below the level needed to maintain an organism's life. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, dea ...

; embryo development is fueled by reserves # the composition of

biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...

depends on growth rate. With two components (reserves and structure) particular changes in composition can be captured. More complex changes require several reserves, as is required for autotrophs. # the body size scaling of life history parameters. The specific respiration rate decreases with (maximum) body size between species because large bodied species have relatively more reserve. Many other life history parameters directly or indirectly relate to respiration. # the observed respiration patterns, which reflect the use of energy. Freshly laid eggs hardly respire, but their respiratory rates increase during development while egg weight decreases. After hatching, however, the respiration rate further increases, while the weight now also increases # all mass fluxes are linear combinations of assimilation, dissipation and growth. If reserves are omitted, there is not enough flexibility to capture product formation and explain indirect calorimetry.

References

Metabolism {{Biochemistry-stub