Biology Reference
In-Depth Information
Density
Demoecology (size/age)
Sex ratio
Genetic diversity
Growth rate
Conditon index
Respiration
Scope for growth
Cellular energy
allocation
Energy
reserves
Adenylate
energy charge
(AEC)
Sub-
cell
Cell
Tissue
Bioenergetic
Individual
Population
Community
Macro
molecule
Level of biological organization
FIGURE 12.1
Biomarkers linked to energy metabolism and bioenergetics, according to the level of biological organization.
• Adenylate energy charge (AEC) assesses the chemical energy necessary for inter-
mediary metabolism.
• Both the energy reserves (glycogen, lipids, proteins) and caloric content indicate
the energy available.
• The cellular energy allocation (CEA) determines the net cellular energy budget.
• The scope for growth (SfG) estimates the net energy budget allocated to the growth
and reproduction of organisms.
• Condition indices provide information on the general condition of organisms.
12.1.1 Adenylate Energy Charge
The AEC is an ubiquitous system in animals and is usually used for assessing the meta-
bolic energy potentially available in a living organism. This endpoint is based on the
measurement of adenosine triphosphate (ATP), adenosine diphosphate, and adenosine
monophosphate (AMP) concentrations (Le Gal et al. 1997). By definition, AEC may vary
from 0 (if all adenylates are stored in the form of AMP) to 1 (if all adenylates are stored
in the form of ATP). In optimal conditions, a steady state between the degradation and
regeneration of ATP is reached, which seems to maintain an AEC value of 0.8 approxi-
mately. The AEC values have been studied in connection with the ability of organisms to
survive, grow, and reproduce. Therefore, in the absence of stress (0.75 < AEC < 0.90), the
growth rate is high, and survival and reproduction are ensured. Under moderate stress
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