Maintenance of an organism is the collection of processes to stay alive, excluding production processes. The
Dynamic Energy Budget
The dynamic energy budget (DEB) theory is a formal metabolic theory which provides a single quantitative framework to dynamically describe the aspects of metabolism (energy and mass budgets) of all living organisms at the individual level, based o ...
theory delineates two classes
* Somatic maintenance mainly comprises the turnover of structural mass (mainly proteins) and the maintenance of concentration gradients of metabolites across membranes (e.g., counteracting leakage). This is related to
maintenance respiration
Maintenance respiration (or maintenance energy) refers to metabolism occurring in an organism that is needed to maintain that organism in a healthy, living state. Maintenance respiration contrasts with growth respiration, which is responsible for ...
.
* Maturity maintenance concerns the maintenance of defence systems (such as the
immune system
The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
), and the preparation of the body for reproduction.
The theory assumes that maturity maintenance costs can be reduced more easily during starvation than somatic maintenance costs. Under extreme starvation conditions, somatic maintenance costs are paid from structural mass, which causes shrinking. Some organism manage to switch to the
turpor
Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...
state under starvation conditions, and reduce their maintenance costs.
Developmental biology
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