Glycolysis is a metabolic process that is employed by all cells, including bacteria, to produce bioenergy. However, glycolysis is not a stand-alone process. Rather it obtains its fuel from photosynthesis. While photosynthesis synthesizes the fuel, glycolysis transforms this biosubstance (glucose) into bioenergy. In such a way, the two processes are time dependent - one following the other. Further both processes are holistic in that they only make sense in relation to the entire cell.
There are 10 steps to the glycolytic process. Each step is a chemical reaction that transforms a biomolecule from one form into another. As high energy biomolecules degrade into lower energy biomolecules, they give off energy. Cells store this energy for discretionary use at a later time. Each step requires an enzyme (a separate biomolecule) to catalyze the chemical reaction. By providing this crucial assistance, enzymes enable the cell to produce energy internally.
Rather than 'enzymatic assistance', biochemists prefer 'enzymatic degradation'. The term 'degradation' focuses our Attention upon the chemical (atomistic) nature of the process, while the term 'assistance' directs our focus to the holistic nature of enzymes. This is significant as the first (degradation) implies scientific determinism, while the second (assistance) implies meaning and purpose, which inevitably points to intelligent design.
The first 5 steps (he first uphill stage) of glycolysis employ internally produced bioenergy to produce a higher energy biomolecule. This initial investment of bioenergy is doubled in the second downhill stage, when the high energy biomolecule degrades into lower energy biomolecules with enzymatic assistance. In brief, by exerting some energy in the beginning, the cell doubles the investment. Rather than relying upon random chemical reactions, glycolysis relies upon a sophisticated and subtle strategy that is designed to serve the needs of the whole cell.
By doing work in its initial (uphill) stage, glycolysis produces the highest energy biomolecule, G3P. As an indication of its importance to the cell, G3P is also the endproduct of photosynthesis. Why so important? This amazing high energy biomolecule can enter a variety of metabolic pathways. If it remains in the glycolytic pathway, cellular respiration extracts the chemical energy stored in its bonds to produce bioenergy. If it enters other pathways, it can become transformed into biomass (glucose), the substance of every living creature. G3P is the source of both biomass and bioenergy, both of which serve the needs of the cell over time.
The cell's strategic employment of its ingredients in a versatile and flexible fashion requires both a temporal and holistic sense - qualities that atoms don't possess. Rather than futilely seeking a material explanation, we must instead look to Life's Information Digestion System to provide explanatory power for these cellular mysteries.
Glycolysis dependent upon Photosynthesis for Fuel
Cells use Energy Released from Enzymatic Degradation to do Work
Degradation? Why not Enzymatic Assistance?
Glycolysis invests Bio-Energy to destabilize Glucose for Splitting
Cells employ G3P to produce both Bio-Mass and Bio-Energy. Amazing!
Let us summarize the two complementary processes that Life employs to generate useable energy. Photosynthesis employs solar energy to convert low energy carbon dioxide and water molecules into high energy glucose. In turn, cellular respiration converts high energy glucose into low energy carbon dioxide. The energy that is given off in this reaction is employed to charge the ATP molecules that power the cell.
Solar energy is transformed into glucose, which is then transformed into useable biological energy. Sounds simple. Not quite. Although there is some overlap, the two processes that create Life’s energy are entirely different, or almost. And both photosynthesis and cellular respiration border on the miraculous.
Let us delve into more detail, starting with glycolysis.
Although technically its own process, glycolysis is, for convenience, called the first stage of cellular respiration. It has 10 steps. Each step requires its own enzyme.
Where are these steps heading? And why does each step require the assistance of an enzyme?
As name implies (‘glyc’=glucose ‘olysis’= splitting apart), this initial process breaks the glucose molecule into smaller molecules. What purpose does this serve?
The complex chemical bonds that hold glucose contain a lot of potential energy. The splitting process releases this stored energy in order to recharge1 ATP molecules. The cell can then use this stored energy to do work – reverse entropy. In this capacity, glucose is the fuel of glycolysis.
Where does glucose come from?
Photosynthesis captures photons from the sun in order to generate glucose’s organic chemical bonds with their stored energy. In other words, photosynthesis supplies the fuel that drives glycolysis. Without photosynthesis, glycolysis is meaningless – like a car without gas – a lightbulb without electricity.
Glycolysis is the beginning of the biological energy creating process. Without photosynthesis-produced glucose virtually all Life forms come to a dead halt. Put another way, plants with their ability to photosynthesize are crucial for Life on Earth.
Hydrolysis’ breaking apart process releases the energy stored in glucose’s molecular bonds. This energy is employed to charge ATP molecules, the cell’s renewable storage battery. In turn, ATP enables the cell to reverse entropy by organizing and powering the metabolic pathways that cells need to survive.
Further the parts that glucose is broken into become the fuel for the Krebs cycle, the next stage of cellular respiration. This process charges even more ATP molecules (18x as many as glycolysis). This increase in potential biological energy is necessary to power all life forms (except single-celled bacteria without a nucleus).
Yet it requires the fuel provided by glycolysis to do its job. Bacteria can survive without cellular respiration. The rest of us with our nucleated cells can’t.
Photosynthesis supplies the fuel for glycolysis, which in turn provides the fuel for cellular respiration, which in turn is required to supply the increased energy requirements for those of us with nucleated cells, i.e. all organisms – plants, animals, and fungi.
While photosynthesis supplies the fuel, it doesn’t convert this fuel into energy. It would be like having gasoline but no engine. Living systems require both photosynthesis and cellular respiration to produce both fuel and energy – the gasoline and the engine.
It is evident that the cell’s energy and mass producing processes are mutually co-dependent – not hierarchical. The question becomes: If they are mutually codependent, how was each able to evolve independently without the other? Rather than sigh our lives away in the attempt to find an answer, it is best to let these mind-bending questions remind us of our ignorance.
Before diving into the specifics of glycolysis, we need to provide some background info regarding a type of energy that cells tap into to do work. This investigation will also provide us with some terminology and knowledge that will enhance communication.
Biologists characterize molecules according to their energy level. High energy molecules have more potential energy in their chemical bonds than do low energy molecules. For cellular energy production, electrons store solar energy in their bonds. These bonds link molecules together as a unit.
The process of photosynthesis transforms low energy carbon dioxide into high energy glucose. It achieves this end by using solar energy coming in the form of photons to create the high energy bonds in glucose’s electrons. In brief, photosynthesis generates a complex, organized molecule from simpler, less organized molecules. It could be said that solar energy is stored in the complex chemical bonds of Bio-molecules – especially the mega-molecules that Life uses for Bio-mass and Bio-energy.
Complex high energy molecules are also less stable due to entropic pressures that seek to equalize energy states. As an indication, high energy molecules such as glucose actually have a half-life. Due to entropy, glucose and other organic molecules naturally degrade over time into lower energy inorganic molecules. This is why fresh food usually provides more energy than stale food. The high energy organic molecules haven’t yet degraded into low energy inorganic molecules.
Every time that a complex molecule degrades into a simpler molecule it releases the energy stored in the electron bonds that have been broken. When this natural entropic degradation occurs, the stored energy that is released is generally dissipated into the atmosphere with no effect.
In contrast, cells employ this released energy of degradation to power some of the chemical reactions in both photosynthesis and the three processes of cellular respiration. The cell regularly uses this degradation energy in a specific fashion to unify and organize its molecules with the purpose of survival and reproduction.
However, the half-life of complex biomolecules is generally too long to be of any use to the cell. In order to take advantage of the energy released through entropic degradation, cells employ enzymes. Enzymes bring the degradation process of complex organic molecules up to the speed of life.
Enzymes are proteins whose sole duty is to lower the activation barrier of specific molecules. Lowering the activation barrier catalyzes the degradation of a higher energy molecule into a lower energy molecule. By catalyzing specific chemical interactions, enzymes speed up the degradation process to a level that is useful to the cell. Due to this unique talent, cells employ enzymes to control the degradation process, i.e. when to turn it on and off.
Recall that the energy that is released when a high energy molecule naturally degrades (due to entropy) into a low energy molecule is generally released into the atmosphere – doing no work. Rather than dissipated into space, the energy that is released in enzymatic degradation is employed to drive the cell’s metabolic pathways – the intricate processes that the cell requires to survive and reproduce. By regulating these chemical interactions via enzymes, cells are able to use the released energy of degradation to do work. Through enzymes, cells can tap into this generally wasted energy of entropic degradation.
Natural Entropic Degradation = No Work
Enzymatic Degradation = Cellular Work
Amazing eh! What magic those little guys can do.
Enzymatic Degradation? What an interesting choice of words. Why not Enzymatic Assistance?
Degradation has negative connotations. For instance, my body is degrading as I approach 75 years of age – certainly not a positive development. Assistance generally has positive connotations, as in I am assisting my students to learn tai chi forms. Further like enzymes, those who assist frequently do not perform the actual work.
The role that enzymes play in the cell’s metabolic pathways is most certainly crucial, hence entirely positive. For instance, enzymes are a key component in cellular energy production. They help chemical reactions to reach an appropriate speed that enable cellular processes to occur in a timely, rather than random, fashion.
With such a decidedly positive contribution to Life, why did biologists use such a negative word as degradation to characterize their role? While it could have been an innocent choice of words, I think not. Degradation of course applies to chemical reactions.
Most of the time, enzymes quicken the speed that complex biomolecules degrade into a simpler state. When they degrade to a simpler state, energy is given off. Rather than dissipate this energy, cells employ it in a constructive fashion. How Presbyterian! However, sometimes enzymes with the assistance of bioenergy assist biomolecules to move to a higher state of complexity and energy. Both of these enzymatic roles are vital to life on Earth.
We suggest that the word degradation was chosen to focus our Attention upon the atomistic chemical reaction, and away from holistic strategy. This exclusively material focus aims ultimately at scientific determinism. The implicit conclusion of this unfortunate mindset: Life is a purely chemical affair.
When the word assistance is employed to characterize the roles of enzymes, it evokes the notion of holistic strategy with a purpose. When we assist elderly people, our holistic strategy has the purpose of making their lives easier, not so difficult. Rather than the atomistic chemical component, the term assistance instead focuses our Attention upon the cell’s holistic nature. The enzyme only has meaning (and purpose) in relationship to the entire cell. Without a cell, an enzyme is just a complex, inanimate molecule without a strategic purpose, without meaning.
Although this difference between atomistic chemical degradation and holistic cellular purpose might seem trivial, virtually every biochemical scientist is acutely aware of the implications. While only a hairbreadth’s difference in the beginning, the contrast between the two types of focus quickly becomes an unbridgeable chasm. From scientific determinism to intelligent design. Horrors! They exclaim. Not realizing that logical science accompanied by greed and the lust for power has wreaked far more havoc on our fair planet in the last few centuries than all the religious wars combined.
We are not going to get into any details here. Suffice it to say that one of the primary intents of this Notebook is to expose the atomistic scientific approach as a fraud when it comes to holistic living behavior. Many material scientists proudly, even arrogantly, cling to their Materialist Dogma, even to the extent of looking down upon those who believe in a higher power as immature. Dressed as they frequently are in their lily-white lab coats (perhaps signifying objectivity), they pretend to ignore all the empirical evidence that contradicts their rigid mindset. Ironically, much of this evidence concerns those aspects of our existence that make Life special, even worth living – our holistic nature.
Ironically these misguided scientists look at a part and think they understand the whole, as with material systems. However in contrast with atomistic Matter, holistic Life’s most significant content and processes only have meaning in relationship to the whole. This is a theme we will be revisiting frequently in this Notebook – providing example after example of Life’s holistic behavior regarding cellular energy production.
Returning to our main topic and shifting to a holistic emphasis, enzymatic assistance is required for every step along the way to the production of biomass and bioenergy.
Now that we have laid the groundwork, let’s look at the specifics of glycolysis. This process, although not technically a part of cellular respiration, is a mandatory perquisite. Why? Glycolysis provides the fuel for the Krebs cycle, the first stage of cellular respiration. Because of this crucial role, many biologists include glycolysis in cellular respiration. For convenience, we do also.
The two formal stages of cellular respiration, the Krebs cycle and the electron transport chain, only occur in mitochondria. This organelle is found in all eukaryotic (nucleated) cells, but not in all prokaryotic (without nucleus) cells. In contrast, the process of glycolysis is shared by every living system, even the prokaryotic bacteria with its relatively rudimentary structure.
Glycolysis is crucial for all life forms, no matter how small. Why? The end product of glycolysis is two ‘charged’ ATP molecules. As mentioned, cells employ the energy stored in ATP’s phosphate bonds to reverse entropy, i.e. organize matter/impart complexity/store information. Without the energy stored in ATP molecules, every living system dies.
This biological fact raises some mystifying questions. From where did the first ATP molecules that powered the first bacterium come? How did this initial bacterium organize itself to create ATP molecules without some ATP molecules to run the process? Bacteria are pretty clever, but how did they self-start themselves?
More perplexing still are questions raised by the 10 steps of glycolysis. For instance, each step requires its own necessary enzyme to catalyze the breakdown of glucose into simpler, lower energy molecules. From where did these enzymes arise? Were these perfect protein configurations just hanging out waiting for the perfect moment to fulfill their destiny?
In the 1950s, scientists demonstrated that organic molecules could have easily self-assembled under the environmental conditions when our Earth was just forming. They thought it would be an easy step to show that organic molecules could evolve into Life. In the ensuing seventy years, the scientific community has yet to accomplish this task.
It is hard to even faintly imagine how ten enzymes just naturally evolved, and then self-arranged themselves in the perfect order to charge ATP molecules. Rather than sigh my life away attempting to explain away this mystery with wild speculations to support preconceived theories, I will just embrace my ignorance. Let us humbly bow down in awe and wonder before this manifestation of some kind of higher power.
The 10 steps of glycolysis themselves are mysterious. The first 5 steps in glycolysis actually generate a more complex, higher energy, less stable molecule. These initial steps both split the 6-carbon glucose molecule in half (hence the name glycolysis) and then add a phosphate group to each of the two resulting 3-carbon molecules. In order to organize the atoms in this way, the cell must spend 2 ATP molecules. An energy investment in a future payoff.
From where did the first bacterium’s initial 2 ATP investment arise? His father? No, she was the first. Perfect in the very beginning and self-replicating ever since. Ever evolving to ultimately generate every life form on the planet. But where did she get her seed capital to get the ball rolling?
The cell’s energy investment eventually pays off quite well. After the initial expenditure of 2 ATPs, the cell ultimately derives 4 ATP molecules from the final 5 stages of glycolysis. This means a net gain of 2 charged ATPs for the cell to employ to reverse entropy – to organize incoming and outgoing molecules, electrons, and protons with the aim of survival of the mysterious collective. Although not nearly as much energy as derived from the next stages of cellular respiration, these storage batteries charged through glycolysis alone has powered and continues to power certain kinds bacteria for billions of years.
It is easy to miss the wonder and get lost in the details of the process. Let us focus upon the amazingly clever nature of the bacteria’s glycolytic process for breaking down glucose.
If a ball is at the bottom of a hill, it is in a state of equilibrium with no potential energy. It takes energy to push the ball up the hill. However, when the ball is at the top of the hill, the pushing energy is stored as the ball’s potential energy due its location. If one pushed the ball, it would naturally roll down to the bottom of the hill. In doing so, it would give up its potential energy.
This is a good metaphor for understanding the entropic nature of metabolic processes. Biologists frequently speak about pushing chemical reactions uphill (in which case, it needs energy) or helping a reaction to run downhill (in which case no energy is required).
The first 5 steps of hydrolysis are uphill, hence require ATP molecules. The second 5 steps are downhill, hence no energy requirement. Although no ATP molecules, the downhill steps do require catalytic enzymes to bring their reactions up to the speed of life.
The very first bacterium was quite clever. She pushed the initial reaction uphill to impart more potential energy to the glucose molecule. This extra energy destabilized the molecule in order to split it into a more useable form. It is a martial move. Push your opponent one way. When they resist, go with the energy and pull them the opposite way to unbalance their equilibrium. How did the first bacterium come up with this sophisticated push-pull strategy to produce enough energy to get her through the day – run her myriad metabolic pathways and such? Through meditation?
We can use this uphill/downhill metaphor to better understand the entire biological substance to energy process, i.e. photosynthesis to cellular respiration. We can imagine the high energy glucose molecule to be stuck in a bowl-like indentation at the top of a mountain. It possesses a lot of potential energy. However, to tap into this energy, the molecule must be first pushed up over the ridge of its bowl before it can begin rolling downhill. Only when it is in its enzyme-controlled roll down the hill can our bacterium or any cell transform the glucose’s potential energy into a useable form, e.g. ATP.
The first 5 steps of glycolysis perform the task of pushing the glucose molecule up out of the bowl’s indentation onto the ridge, so that it can begin moving downhill. However, our metaphor breaks down at this point. Our metaphoric ball with its fixed mass must be transformed into a new kind of ball to go up our metaphoric hill. Through glycolysis, the cell rearranges the actual atomic structure of the glucose molecule. Pretty amazing eh? Way more than high school chemistry. Rather every cell is performing cutting edge biochemistry – something for doctoral or post doc candidates.
In its first 5 steps, glycolysis rearranges the carbon ring of glucose to produce sucrose. This nearly universal cellular process also adds phosphate groups to produce new types of molecules. The result is an unstable 6 carbon molecule of sucrose. It is so unstable that the last step of this initial phase (with the help of an enzyme) is able to split 6 carbon sucrose into two 3 carbon molecules. G3P is the name of the highest energy, but unstable molecule, at the top of the ridge.
From this precarious ridge, the G3P can roll downhill in two different directions. One direction produces biological energy; the other produces biological substance.
If G3P remains in the glycolytic metabolic pathway, it can move downhill to store biological energy for the cell’s discretionary use at a later time. Glucose’s potential energy is used to charge some ATP molecules and load up a special molecule NADH with an electron’s energy. The cell uses NADH to transport the energy of electrons to do work. When the process reaches the glycolytic bottom, the end product is pyruvate. Pyruvate is the fuel for cellular respiration, which produces even more ATP.
G3P is also the end product of photosynthesis. In this case, the G3P molecule can be converted into biological substance such as glucose or sucrose. This is the stuff, the matter, the material of living systems. It allows us to grow bigger, acquire more mass, put on weight. It is the organic material that comprises the mighty Sequoia as well as the tiny spider. Of course, the stored energy in this organic material also provides the food, the sustenance, the nutrition for all life on earth.
In summary, the cell employs this high energy G3P molecule to both create biological energy and substance. Quite versatile. The middle product of glycolysis and the end product of photosynthesis. Amazingly ingenious. Dual purpose.
Bow your head in awe, humility and wonder before the elegant simplicity and complexity of Nature’s most basic living process.
1 Technically, the ATP molecule (Adenine Tri (3) Phosphate) is created (not recharged) when a phosphate group is added to an ADP molecule (Adenine Di (2) Phosphate) in a chemical process. Alternately when ATriP does work for the cell, it loses this phosphate group and becomes ADiP. This cyclic all-or-nothing affair employs pre-made compounds to cycle between ADP and ATP. More assemblage; less creation. The Adenine-Phosphate complex acts like storage battery – alternating between 3 phosphate groups in its charged state and 2 phosphate groups in its uncharged state. As such, I prefer to think as ATP being recharged rather than created.