Physical Approaches to Metabolic Scaling in Living Systems

TL;DR

This review explores physical and thermodynamic principles underlying metabolic scaling in living systems, synthesizing empirical data and models to understand how metabolic rates relate to organism size across biological levels.

Contribution

It provides a comprehensive interdisciplinary synthesis of empirical findings and theoretical models on metabolic scaling, emphasizing physical concepts and recent advances in the field.

Findings

Multiple metabolic scaling patterns observed at different biological levels

Biophysical models explain sublinear scaling of metabolic rate

Recent advances include developmental metabolism studies

Abstract

Living systems continuously transform matter and energy through the chemical processes that constitute their metabolism. The overall metabolic rate of an organism correlates positively with its body mass, however both the exact scaling behavior and possible explanations for this behavior have been under intense debate for two centuries. This review synthesizes empirical findings and theoretical frameworks on the energetics of living systems from an interdisciplinary perspective, with a focus on physical concepts. A general thermodynamic framework to study metabolism is laid out, together with a coarse-grained description of metabolic biochemistry. The rich history of experimental work in this field is surveyed, revealing a variety of metabolic scaling patterns at different levels of biological organization, from individual cells to whole populations. Several biophysical models proposed to explain the sublinear scaling of metabolic rate with body mass are summarized. Though the traditional focus has been on adult organisms, the review also highlights recent advances that probe metabolism during development. Improvements in experimental techniques, extensive datasets, and a host of open questions, suggest the field will continue gaining momentum in the near term. The review concludes with an outlook for this future progress: an interdisciplinary approach to elucidate metabolic scaling across different developmental stages and organism sizes.