At this very moment, you are delicately balanced on the thin line between life and death. Although you might not perceive it, an extraordinary amount of activity is happening within you, and this activity must never cease. Imagine yourself as a Slinky descending an upward-moving escalator. The descent symbolizes the self-replicating processes of your cells, while the escalator represents the laws of physics propelling you forward. To be alive is to be in perpetual motion without ever reaching a final destination. Should you reach the top of the escalator, the journey ends, and you are forever still. The universe, somewhat unsettlingly, seems to prefer this stillness. So, how do you avoid it? And why are you alive?
All life is fundamentally based on the cell. A cell is a fragment of the inanimate universe that has separated itself to pursue its own existence temporarily. When this separation fails, it perishes and rejoins the inanimate universe. Unfortunately, the universe appears to favor the cessation of life’s activities. It seems to prefer monotony over excitement, a principle we know as “entropy.” This fundamental rule of our universe is complex and counterintuitive, but for now, it’s enough to understand that living beings are inherently dynamic and exciting.
A cell is teeming with millions of proteins and even more simple molecules like water. Thousands of complex, self-replicating processes occur up to hundreds of thousands of times every second. To remain alive and vibrant, a cell must continually work to prevent itself from succumbing to entropy and becoming inert. It maintains a separation from the rest of the universe by, for example, actively pumping out excess molecules to keep the concentration of certain molecules different inside and outside. To perform such tasks, a cell requires energy.
Energy is the universe’s ability to perform work, to move or manipulate objects, and to create change. This ability cannot be created or destroyed, and the total amount of energy in the universe remains constant. We don’t know why this is the case, but it simply is. Billions of years ago, one of the first living beings’ most critical challenges was acquiring usable energy. Although we know little about the first cells, we understand that they derived energy from simple chemical reactions. They discovered the ultimate energy transfer system: the molecule Adenosine Triphosphate, or ATP.
ATP’s structure makes it exceptionally efficient at accepting and releasing energy. When a cell requires energy, for instance, to expel molecules or repair a broken micro-machine, it can break down ATP and use the chemical energy to perform work and create change. This capability is why living beings can accomplish tasks. While we don’t know when or how the first ATP molecule was formed on Earth, every known living organism uses ATP or a similar molecule to keep its internal machinery running. It is crucial for nearly every process necessary for survival.
While early life forms relied on chemical reactions for energy, they missed out on the most abundant energy source: the Sun. The Sun fuses atoms and emits photons that carry energy into the solar system. However, this energy is raw and indigestible, requiring refinement. After hundreds of millions of years of evolution, a cell finally learned to harness the Sun’s energy through a process called photosynthesis. This process converts electromagnetic energy into chemical energy stored in ATP molecules, eventually leading to the creation of glucose, a high-energy sugar.
Some cells decided to bypass the labor of photosynthesis by consuming other cells that performed it, taking their glucose and ATP. This evolutionary strategy is considered one of the most significant betrayals in history. Over time, some cells made sugar, while others consumed them. Evolution continued its course, but overall, things remained relatively unchanged for hundreds of millions of years. Then, one day, a cell consumed another without killing it, leading to a monumental change.
This event marked the beginning of complex life on Earth. The consumed cell became the mitochondria, the powerhouse of the host cell, focusing solely on producing ATP. This division of labor provided the new cell with more energy than ever before, opening up new evolutionary possibilities and eventually leading to multicellular life forms, including humans.
Today, you are a complex organism composed of trillions of cells, each filled with numerous machines that provide the energy necessary for life. If this energy production is interrupted, even briefly, life ceases. While storing ATP like we store sugar in fat cells might seem prudent, it’s impractical. ATP is excellent for quick energy transfer but inefficient for storage. Thus, ATP is constantly produced and consumed.
This is the story of ATP, the molecule that allows you to remain distinct from the inanimate universe, much like a Slinky on an escalator. It’s a peculiar tale of survival, where you must continually produce your own fuel to keep moving. This journey began billions of years ago when parts of the inanimate universe came together to form something new, setting the Slinky in motion. From the first cells to you, this motion has persisted. Eventually, you will rejoin the inanimate universe, but until then, you have the opportunity to make life more interesting.
Create a 3D model of a cell using everyday materials. Focus on illustrating the cell’s components involved in energy production, such as mitochondria and ATP molecules. Present your model to the class, explaining how each part contributes to the cell’s battle against entropy.
Conduct an experiment to demonstrate energy transfer. Use a simple setup like a battery-powered motor to show how energy is converted from one form to another. Relate this to how cells convert energy from ATP to perform work, drawing parallels to the processes discussed in the article.
Participate in a simulation game that models the process of photosynthesis. Your goal is to optimize energy capture from sunlight and convert it into chemical energy. Reflect on the challenges faced by early life forms in harnessing solar energy and how this process has evolved.
Engage in a class debate on the evolutionary strategies of cells, such as photosynthesis versus consumption of other cells. Discuss the advantages and disadvantages of each strategy and how these choices have shaped the evolution of life on Earth.
Join a group discussion on the concept of entropy and its implications for life. Explore how living organisms maintain order and resist entropy. Share your thoughts on the balance between existence and the universe’s tendency towards stillness, as described in the article.
Cell – The basic structural, functional, and biological unit of all living organisms, often considered the building block of life. – The human body is composed of trillions of cells, each performing unique functions essential for survival.
Energy – The capacity to do work or produce change, which can exist in various forms such as kinetic, potential, thermal, and chemical. – Plants convert solar energy into chemical energy through the process of photosynthesis.
ATP – Adenosine triphosphate, a molecule that carries energy within cells and is essential for cellular processes. – During cellular respiration, glucose is broken down to produce ATP, which powers cellular activities.
Entropy – A measure of the disorder or randomness in a system, often associated with the second law of thermodynamics. – As entropy increases in a closed system, the energy available to do work decreases.
Photosynthesis – The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll. – Photosynthesis converts carbon dioxide and water into glucose and oxygen, providing energy for plant growth.
Molecules – Groups of two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound. – Water molecules consist of two hydrogen atoms bonded to one oxygen atom.
Universe – The totality of known or supposed objects and phenomena throughout space; the cosmos. – The laws of physics apply universally, governing the behavior of matter and energy throughout the universe.
Evolution – The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth. – Charles Darwin’s theory of evolution explains how species adapt over time through natural selection.
Life – A characteristic that distinguishes physical entities with biological processes from those without, such as growth, reproduction, and response to stimuli. – Scientists study the conditions necessary for life to understand how organisms thrive in various environments.
Glucose – A simple sugar that is an important energy source in living organisms and a component of many carbohydrates. – Glucose is a primary energy source for cells and is crucial for cellular respiration.
