Free & Unfree Energy
The Bioenergetic Blueprint #02
NB: This article is part of the Bioenergetic Blueprint series. The series is meant to be read in order. You can find its table of contents right here.
In the previous article, we learned that energy can be harvested to oppose the entropic tendency of the universe; and that it exists, simultaneously, as a property of physical substances, since matter incorporates energy into its very structure. We learned that this process is at the core of life.
In parallel, we met the first and second laws of thermodynamics, all the while acknowledging that they are descriptions—and not prescriptions—of universal phenomena. Here they are, as a reminder:
The universe contains a constant amount of energy; energy is never created nor destroyed, merely transformed.
The entropy (i.e., disorder) in the universe is always increasing, and in any given system the same will happen unless energy is spent in maintaining order.
With all of that said, let me ask you:
If the universe’s energy remains constant, how can disorder increase? Doesn’t more disorder imply less energy? Shouldn’t there always be enough energy to counteract disorder?
The answer to these questions lies behind a hidden fact, namely, that not all energy is considered equal. So, even though the total energy in the universe might always be constant, not all of it can be used to counterbalance the increasing entropy. For that, you need the right type of energy.
Free and Unfree Energy
All energy in a given system can be subdivided into two broad categories:
Free Energy: Energy free to do work.
Unfree Energy (often referred to as “dispersed heat”): Energy not free to do work anymore.
As an analogy, think of light. Whenever you light up a lightbulb, a portion of the light produced will be useful to you, and the rest will leak out of your windows, scatter into the atmosphere, and thus become unusable.
Similarly, when a system uses energy to perform a task, not all of it is used efficiently. A portion of the energy is usually allocated to the task at hand, while the rest is simply “lost,” mostly as heat. This energy leakage exists because energy conversion processes are never 100% efficient.
Two simple examples:
A car engine burns energy-dense fuel to produce motion, but not all of it is allocated efficiently: some of the energy from the fuel doesn't contribute to moving the car and is instead “lost” as heat, which is why engines get hot.
Similarly, a laptop uses electrical energy to operate, but again, not all this energy is used for computing tasks: some of it is “lost” as heat, which is why laptops become warmer during use (or scorching hot, depending on your budget).
Anyway, a similar leaking phenomenon occurs when biological organisms burn fuel (like glucose) for energy, but often in a much more efficient and sophisticated way.
Your cells use a lot of energy from food to perform non-spontaneous processes, such as assembling particular molecules. In doing so, some of the energy being converted is lost as heat. The more energy your body processes, the more heat it radiates—and thus the hotter your body temperature gets. In times of acute energy demands, we call this a fever.1
This is why organisms with a fast metabolism—meaning, whose cells are consuming high amounts of energy—have higher body temperatures. Bears have higher body temperatures in the summer (when they are active with hunting, reproducing, etc.) than in the winter (when food is scarce and they hibernate to minimize energy use).
The heat you, I, bears, and many other organisms radiate is considered to be unfree energy because it cannot be gathered to do work anymore. Once it is dispersed into the atmosphere, it contributes to the random and chaotic motions of molecules in the universe: it contributes to the latent rise of entropy.
People often get confused by this, because free energy ironically seems to be the one “confined” in a specific actor, and unfree energy the one roaming around “freely”, as heat does. But remember: energy from dispersed heat is very hard to harvest and use again; so, in a way, it is “condemned” to remain scattered up. On the other hand, free energy is free to take this form and that, depending on its fate.
Insightfully, you can flip this perspective on its head and conceive of heat not as a byproduct of energy production, but as the product it ultimately yields. It “just so happens” that the steps produced all along the interim of this grand-scale energy transfer can produce work—a phenomenon living organisms take advantage of.
Remember: Life exists and evolves because, at a fundamental level, matter has managed to (1) interpose itself over the flow of energy and (2) elaborate itself by exploiting its current.
Meet my G
Because there is a difference between free and unfree energy—that is, a difference in the availability of energy—we can measure the net change between one and the other in any given reaction. If we do so, we will realize that some reactions, once completed, will result in a net decrease in free energy, others in a net increase, and the rest in a rough net balance.
Free energy is calculated through what’s known as the Gibb’s Free Energy equation:
Where:
G = Free Energy (energy free to do work)
H = Enthalpy (the total energy in the system)
T = Temperature (in degrees Kelvin)
S = Entropy (a measure of system randomness)
Thus, following Gibb’s, free energy is essentially the total energy in the system, minus the product between entropy and temperature. This implies that higher temperatures lead to more randomness, and that, at absolute zero (T = 0 K), all of the system’s energy is available as free energy, waiting to be unleashed.
What matters most to us here is whether a particular reaction has a positive or negative net effect on G, rather than the individual components of the equation. In other words: we want to know whether the reaction increases or decreases free energy.2
Increase in Free Energy
If, after a particular reaction (in net) free energy has increased, it means free energy has been incorporated into the system. These reactions increase order in the universe because they oppose entropy.
These types of reactions don’t happen spontaneously, as they need an input of energy to occur (known as activation energy). Because of this, they are referred to as “energetically unfavorable” reactions.
We denote the net effect of these reactions as +ΔG, where “Δ” signifies change. This basically translates to “There is more free energy now”.
Decrease in Free Energy
On the other hand, if, after a particular reaction (in net) free energy has decreased, it means free energy has been lost as dispersed heat. These reactions decrease order in the universe because they give in to entropy.
These types of reactions happen spontaneously, as they don’t need an input of energy to occur. Because of this, they are referred to as “energetically favorable” reactions.
We denote the net effect of these reactions as -ΔG, which, as you can imagine, basically means “There is less free energy now.”3
Let’s look at both of these effects in context through a couple of examples:
Sisyphus and the Boulder
When Sisyphus rolls a boulder up a hill…
He is increasing free energy because he is spending energy and incorporating it into the boulder.
He is performing an energetically unfavorable task by pushing the boulder against its energetic equilibrium (i.e., resting down the hill).
The whole process has a +ΔG: an increase in energy free to do work, which is now “contained” in the boulder. Conversely, we can think of this process as resulting in a decrease in disorder.
When the boulder falls down the hill…
There is a decrease in free energy, because no energy is being spent for it to happen, but is rather being released into the environment as kinetic energy (through the movement of the boulder), thermal energy (through friction against air and ground), etc.
This is an energetically favorable task because the boulder is going towards its energetic equilibrium.
The whole process has a -ΔG: a decrease in energy free to do work, which has been liberated into the surroundings. Conversely, we can think of this process as resulting in an increase in disorder.
And let me give one final example, for clarity:
Constructing a Building
Constructing a building implies an increase in free energy: an increase in energy able to make things happen.
When constructing, workers incorporate all sorts of energy (mechanical, kinetic, chemical) into the building itself. This construction process increases order in the universe because it puts elements that were once scattered around into a non-spontaneous shape.
This is a very energetically unfavorable task, which is why you need (paid) workers to make it happen. The building itself is now a high-free-energy entity because it “holds” within it a ton of potential for change: a ton of incorporated free energy.
The whole process has a +ΔG: an increase in energy free to do work; or, conversely, a decrease in disorder.
On the other hand, a building collapsing on itself implies a decrease in free energy.
When collapsing, energy is violently released from the building onto its environment, spontaneously throwing its components around.
This is an energetically favorable task because the building is returning to a lower free energy state, one in which fewer things can happen to it. The collapsed building is now a relatively low-free-energy entity because it “holds” within it less potential for change than it did before.
The whole process has a -ΔG: a decrease in energy free to do work; or, conversely, an increase in disorder.
Conclusion
This whole building-up and tearing-down process is quite similar to the two main types of reactions that take place within our bodies.
Reactions that build things up (e.g., making complex molecules from simple molecules and/or single atoms) are called anabolic reactions, from the Greek anabolē: to throw upwards. These are, as you might expect by now, energetically unfavorable (+ΔG), just as throwing a ball upwards requires effort.
Reactions that tear things down (e.g., breaking down big molecules into tinier molecules) are called catabolic reactions, from the Greek kataballein: to throw downwards. These are, in part, much more energetically favorable (-ΔG), just as throwing a ball downwards requires no effort.
If you sum up all anabolic and catabolic reactions inside your body, you get what’s called your metabolism.
I know these things can be a bit annoying to wrap your head around at first, but I wanted to cover them here because they'll make subsequent articles clearer and more meaningful.
If you have any questions and/or suggestions, feel free to leave them below.
Upwards,
Yago
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Fevers don’t only take place as a byproduct of the increased metabolic rate. They are also deliberately produced by your body (e.g., through “futile cycling”, where two opposing reactions occur simultaneously, leading to energy expenditure without net production of metabolic products, thus “just” generating heat). This is done to (1) establish an inhospitable environment for pathogens and (2) increase the overall energy in the system, thus making particularly energy-demanding, non-spontaneous reactions more likely to happen by reducing their relative activation energy.
Please note that, technically, Gibb’s Free Energy measures the maximum reversible work that may be performed by a thermodynamic system at a constant temperature and pressure—specifics which are too pedantic to cover here.
Don’t let deltas and letters confuse you:
+ΔG just means the change (Δ) in free energy (G) has been positive (+); it has gone up.
-ΔG just means the change (Δ) in free energy (G) has been negative (-); it has gone down.