Feynman’s Whispers of Life: The Dance of Atoms in Biology

In his iconic Lectures on Physics, Richard Feynman offers a fascinating exploration of the intersection between physics and biology, illustrating how these disciplines interconnect to unravel the mysteries of life. Feynman’s ability to bridge these seemingly distinct fields reveals the elegance and complexity of the natural world, where the “jigglings and wigglings of atoms” underpin even the most intricate biological processes.

The Early Interplay of Physics and Biology

Feynman begins by recounting how early biology was rooted in description—categorising living organisms and their observable characteristics, such as the hairs on the limbs of fleas. However, as biology matured, it moved toward understanding the “machinery” within living organisms. Interestingly, biology contributed to physics early on through the discovery of the conservation of energy. Julius Robert Mayer’s experiments involving the heat exchanged by living creatures provided critical insights into this fundamental law. Here, Feynman sets the stage for a recurring theme: biological phenomena are deeply intertwined with physical principles.

Nerves, Capacitors, and Dominoes: Physics in Action

One of Feynman’s most vivid analogies describes the transmission of nerve impulses, likening it to a row of dominoes toppling sequentially. He explains that nerves are essentially fine tubes with a thin, ion-pumping membrane. This membrane creates a voltage difference, much like a capacitor, by separating positive ions outside from negative ions inside. When the nerve “discharges” at one point, the disturbance propagates along the membrane, similar to how a domino pushes its neighbour. This wave of electrical activity transmits signals, such as the sensation of stepping on a sharp stone. The image of dominoes falling—sequential, elegant, and self-repeating—demonstrates how physics illuminates biological functions.

Equally fascinating is how this process resets. Just as dominoes must be stood up again for a new wave to propagate, nerve cells actively pump ions back to their original positions, preparing for the next signal. This interplay between electrical physics and biology showcases how disciplines converge to explain complex systems.

Muscles, Molecules, and Enzymes

Feynman next delves into the mechanics of muscles, explaining how electrical signals from nerves trigger muscle contraction. The process involves the release of acetylcholine, a chemical messenger, which induces a cascade of reactions within muscle fibres. At the molecular level, proteins like myosin and actomyosin interact to produce motion, though the exact mechanisms remain elusive.

Here, Feynman introduces the concept of enzymes—large protein molecules that facilitate chemical reactions by lowering the energy barriers between reactants. He compares this to physically pushing an object over a hill to reach its destination. Enzymes, however, provide a “shortcut,” enabling reactions to occur without requiring excessive energy. This analogy, combined with descriptions of enzymes as “machines in a factory,” underscores their precision and importance in sustaining life.

The Molecular Machinery of Life

At the heart of living systems are cells, where a complex interplay of biochemical reactions takes place. Feynman highlights the Krebs cycle, a series of chemical transformations that generate energy. He uses the analogy of “activation energy hills” to explain why certain reactions require energy input. Enzymes, as specialised tools, help molecules bypass these barriers, allowing life’s processes to unfold efficiently.

One of the most compelling aspects of this discussion is the energy currency of cells: guanine triphosphate (GTP). Feynman describes GTP as an “energy-carrying box” that drives cellular activities, such as muscle contraction. The reversible transformation between GTP and GDP exemplifies the elegant balance of energy flow in living systems.

The Blueprint of Life: DNA

Feynman’s exploration of DNA marks a shift from molecular machinery to the genetic code that governs life. DNA, he explains, is a double helix composed of two complementary chains. The sequence of its four base pairs—adenine (A), thymine (T), cytosine (C), and guanine (G)—encodes the instructions for building proteins. The pairing rules (A with T, C with G) allow DNA to replicate itself during cell division, ensuring the continuity of life.

Feynman’s imagery shines here: he describes DNA as a “blueprint” capable of duplicating itself through a clever molecular mechanism. Each chain serves as a template for assembling its complement, enabling precise replication. However, he notes that the exact process by which DNA instructs the formation of proteins remains a central mystery in biology.

Physics as a Tool for Biology

Throughout the lecture, Feynman emphasises the indispensable role of physics in advancing biology. Techniques such as isotope labelling allow scientists to trace the pathways of chemical reactions, providing a clearer picture of cellular processes. The ability to “label” atoms and track their movements has been crucial in constructing biochemical pathways, such as the Krebs cycle.

The Unifying Vision

Feynman concludes by reflecting on the broader implications of this interdisciplinary approach. Biology, for all its complexity, can ultimately be understood through the principles of physics—atoms, energy, and motion. This perspective highlights the unity of science, where discoveries in one field enrich understanding in another.

By weaving vivid analogies and profound insights, Feynman transforms the intricate relationship between physics and biology into an accessible and inspiring narrative. His lecture reminds us that the natural world operates as a harmonious system, where the same fundamental laws govern both the smallest particles and the grandest phenomena of life.