# The free lunch of a scale-free metabolism

## TL;DR

This paper demonstrates that apparent scale-free patterns in metabolic fluxes are artifacts caused by thermodynamically unfeasible cycles, and correcting for these reveals a more meaningful, constrained metabolic space with complex structure.

## Contribution

It identifies the source of scale-free tails in metabolic flux data as thermodynamic artifacts and proposes a correction method revealing the true constrained metabolic space.

## Key findings

- Scale-free tails are artifacts of unfeasible cycles.
- Correcting thermodynamics reveals a constrained, multimodal metabolic space.
- Metabolic space scales with physical limits after correction.

## Abstract

In this work it is shown that scale free tails in metabolic flux distributions inferred from realistic large scale models can be simply an artefact due to reactions involved in thermodynamically unfeasible cycles, that are unbounded by physical constraints and would be able to perform work without expenditure of free energy. After correcting for thermodynamics, the metabolic space scales meaningfully with the physical limiting factors, acquiring in turn a richer multimodal structure potentially leading to symmetry breaking while optimizing for objective functions.