# Key biology you should have learned in physics class: Using ideal-gas mixtures to understand biomolecular machines

## TL;DR

This paper uses ideal-gas mixture thermodynamics and chemical kinetics to explain key cellular transport processes, providing insights into biomolecular machinery and energy use in biological cells.

## Contribution

It introduces a simple theoretical framework combining thermodynamics and kinetics to understand cellular transport mechanisms, emphasizing non-equilibrium aspects.

## Key findings

- Thermodynamic principles clarify molecular import/export in cells.
- Mass-action kinetics provide detailed insights into transporter function.
- ATP's role links chemical details to physical transport models.

## Abstract

The biological cell exhibits a fantastic range of behaviors, but ultimately these are governed by a handful of physical and chemical principles. Here we explore simple theory, known for decades and based on the simple thermodynamics of mixtures of ideal gases, which illuminates several key functions performed within the cell. Our focus is the free-energy-driven import and export of molecules, such as nutrients and other vital compounds, via transporter proteins. Complementary to a thermodynamic picture is a description of transporters via "mass-action" chemical kinetics, which lends further insights into biological machinery and free energy use. Both thermodynamic and kinetic descriptions can shed light on the fundamental non-equilibrium aspects of transport. On the whole, our biochemical-physics discussion will remain agnostic to chemical details, but we will see how such details ultimately enter a physical description through the example of the cellular fuel ATP.