The cell: a molecular Rube Goldberg machine

Kayla Harnist
Jan 5
4 min read

Writer: Kayla Harnist

Editors: Sam Alper, Courtney Demmit-Rice, Michelle Norman

Illustrator: Aimee Szymanski

Do you ever wonder how the cells in a flower know when to turn from a bud to a bloom? This seemingly simple task begins in a mechanistically complex way. To ensure that a flower blooms just as spring arrives, each cell in a plant must carefully read and respond to its environment. This intricate molecular choreography is analogous to the inventions of Rube Goldberg. Rube Goldberg was a twentieth century cartoonist whose drawings depicted ridiculous contraptions that solve obvious problems in inefficient ways. His cartoons became so iconic his name would inspire the term “Rube Goldberg machine”. To understand the spirit of his invention, imagine a machine designed to pour your breakfast cereal. A cuckoo clock rings your morning alarm while simultaneously striking a marble into motion. The marble, rolling down a track, gathers speed until it topples over a train of dominoes that sets into motion an intricate chain of events. At the end of this absurd sequence, a lever tips a milk carton into your waiting bowl — just as you roll out of bed. Much like this elaborate (but admittedly impressive) way to make breakfast, the cell relies on its own Rube Goldberg-like machines in the form of protein cascades to carry out the functions of complex decision-making necessary to life.

What proteins make up these pathways and how do they work?

Similar to the cuckoo clock that sets the marble into motion at the start of our Rube Goldberg machine, a chain of events inside a cell can begin with a simple nudge. For many pathways, the trigger is a signaling molecule — a small messenger that tells the cell when it’s time to grow or divide. A signaling cascade begins when a signaling molecule alerts a protein at the cell’s surface. Like a falling line of dominoes, this protein will alert a secondary messenger protein that alerts another messenger protein, which alerts yet another, and so on.

Take Sonic Hedgehog for example. Sure, you could imagine the speedy blue hedgehog from your favorite video game growing up, but this is also the real name of a signaling molecule used in cellular processes like division and growth. In this pathway, Sonic Hedgehog starts the chain of communication setting off a series of messenger handoffs from one protein to the next. Eventually, this cascade will reach the cell’s control center: the nucleus. There, the cell interprets the message and decides what to do next. Will it divide? Will it build something new? Or maybe it will choose to do something entirely different. The nucleus may have the final say in what a cell will do, but often the outcome is not reliant on a single pathway — cellular signaling machinery rarely runs in isolation.

In reality, signaling cascades are made up of numerous Rube Goldberg-like machines where each one helps determine what the cell will do next. It’s like having two separate trains of dominos converge to perform the same task. If one train of dominos fails to topple over, the second one can recover and continue the cascade. The redundancy built into these networks ensures that a cell has all the necessary resources and support it needs to carry out instructions precisely. Even the Sonic Hedgehog pathway does not work alone. At least six other pathways weigh in before the Sonic Hedgehog signal even reaches the nucleus, helping refine the final outcome of the cell. Timing and coordination matter just as much as the sequence of events itself. Think back to our morning bowl of cereal — if our contraption is set off too soon, we will have soggy cereal and warm milk by the time we get out of bed in the morning. Even worse, if our signaling machine fails at any point in the cascade, we will not have breakfast at all, and no one wants that!

When it all goes wrong

Unfortunately for the cell, the consequence of failure is much more severe than the status of your morning bowl of cereal. When these signaling cascades fail, the resulting lack of control can lead to disease. Luckily redundancy ensures that the breakdown of cell signaling cascades is the result of multiple smaller failures rather than a single catastrophic one, highlighting both the complexity and coordination of these systems. However, these small errors can accumulate over time. If a few too many dominos fail to fall into place, our signaling pathway is no longer regulated, leading to some harsh outcomes: maybe our cereal bowl overfills or is never filled at all. For the cell, this translates to outcomes like uncontrolled cell growth which can lead to things such as cancer.

Beauty in the design

A single cellular signaling cascade does not provide enough information alone for a cell to make informed decisions about how to respond to a given environment. One cereal-making Rube Goldberg machine, for example, is not sufficient to complete all your daily tasks. You also need to get dressed, brush your teeth, and make it through morning traffic to get to work on time. Similarly, the cell utilizes numerous signaling cascades all at once to survey the many different aspects of its environment to make decisions. Clearly, conceptualizing the processing power of a cell is no easy task; could you imagine setting up a Rube Goldberg machine on par with the capability of a cell? As a scientist, this knowledge serves as a subtle everyday reminder of the complexity of life and an appreciation for the beauty in the design, something that every person should have. But you don’t need to be a scientist to appreciate the sheer complexity of it all. The hidden machinery behind something as simple as a flower in bloom is reminder enough to remain in awe of life’s intricacies.