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DOI: 10.1201/9781003336433-2

2

Orientation for the

Bio-​Curious

The Basics of Biology for the Physical

Scientist

If you want to understand function, study structure. [I was supposed to have said in my

molecular biology days.]

—​Francis Crick, What Mad Pursuit: A Personal View

of Scientific Discovery (1988, p. 150)

General Idea: This chapter outlines the essential details of the life sciences that physical

scientists need to get to grips with, including the architecture of organisms, tissues, cells, and

biomolecules as well as the core concepts of processes such as the central dogma of molecular

biology, and discusses the key differences in the scientific terminology of physical parameters.

2.1  INTRODUCTION: THE MATERIAL STUFF OF LIFE

The material properties of living things for many physical scientists can be summarized as

those of soft condensed matter. This phrase describes a range of physical states that in essence

are relatively easily transformed or deformed by thermal energy fluctuations at or around

room temperature. This means that the free energy scale of transitions between different

physical states of the soft condensed matter is similar to those of the thermal reservoir of the

system, namely, that of ∼kBT, where kB is the Boltzmann constant of 1.38 × 10⁻²³ m² kg s⁻² K⁻¹

at absolute temperature T. In the case of this living soft condensed matter, the thermal res­

ervoir can be treated as the surrounding water solvent environment. However, a key feature

of living soft matter is that it is not in thermal equilibrium with this water solvent reservoir.

Biological matter, rather, is composed of structures that require an external energy input to

be sustained. Without knowing anything about the fine details of the structures or the types

of energy inputs, this means that the system can be treated as an example of nonequilibrium

statistical thermodynamics. The only example of biological soft condensed matter, which is

in a state of thermal equilibrium, is something that is dead.

KEY POINT 2.1

Thermal equilibrium =​ death

Much insight can be gained by modeling biological material as a subset of nonequilibrium

soft condensed matter, but the key weakness of this approach lies in the coarse graining and

statistical nature of such approximations. For example, to apply the techniques of statistical