An energy balance concept for habitability
An energy balance concept for habitability
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DOI：
10.1089/ast.2006.0095
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发表时间：
2007-12-01
期刊：
影响因子：
4.2
通讯作者：
Hoehler, Tori M.
中科院分区：
文献类型：
--
作者：
Hoehler, Tori M.
可居住性可以表述为生物对能量的需求与通过将能量从环境转换到生物过程来满足该需求的相应潜力之间的平衡。生物对能量的需求表现为两个要求，类似于电气设备的电压和功率要求，如果要维持生命，必须满足这两个要求。这些要求表现出离散（非零）的最小值，其大小是由生物化学的问题，他们增加了量化的方式（i）偏离生物化学最佳的物理和化学条件和（ii）能源消耗的解决方案的资源限制的问题。能量转换的可能速率受到以下因素的限制：（i）环境中可用的自由能量源的可用性，（ii）这些能量源运输到细胞中的限制，（iii）能量可以被储存、运输和随后通过生化机制释放的速率的上限（例如，例如，在一个实施例中，酶饱和效应），和（iv）不能使用导致材料击穿的水平的“功率”和“电压”所施加的上限。当能量转换的实现速率等于或超过生物对能量的需求时，系统是可居住的。对于水的可用性被认为是可居住性的一个关键方面的系统（例如，例如，在一个实施例中，火星），能量平衡结构施加了额外的定量约束，这可能有助于在生命搜索任务中优先考虑目标。由于生物对能量的需求是普遍的，能量平衡结构也有助于限制系统的可居住性（例如，例如，在一个实施例中，设想使用除水以外的溶剂的那些），对于这些溶剂目前几乎不存在限制。
Habitability can be formulated as a balance between the biological demand for energy and the corresponding potential for meeting that demand by transduction of energy from the environment into biological process. The biological demand for energy is manifest in two requirements, analogous to the voltage and power requirements of an electrical device, which must both be met if life is to be supported. These requirements exhibit discrete (non-zero) minima whose magnitude is set by the biochemistry in question, and they are increased in quantifiable fashion by (i) deviations from biochemically optimal physical and chemical conditions and (ii) energy-expending solutions to problems of resource limitation. The possible rate of energy transduction is constrained by (i) the availability of usable free energy sources in the environment, (ii) limitations on transport of those sources into the cell, (iii) upper limits on the rate at which energy can be stored, transported, and subsequently liberated by biochemical mechanisms (e. g., enzyme saturation effects), and (iv) upper limits imposed by an inability to use "power" and "voltage" at levels that cause material breakdown. A system is habitable when the realized rate of energy transduction equals or exceeds the biological demand for energy. For systems in which water availability is considered a key aspect of habitability (e. g., Mars), the energy balance construct imposes additional, quantitative constraints that may help to prioritize targets in search-for-life missions. Because the biological need for energy is universal, the energy balance construct also helps to constrain habitability in systems (e. g., those envisioned to use solvents other than water) for which little constraint currently exists.