Welcome to "Biology 101," where today's topic is "What is Adenosine Triphosphate?" pronounced, "Ah-DEN-oh-seen Try-FOS-fate" or ATP for short.
If you happened to stumble on this page because you meant to go to Wikipedia's definition of it, don't leave just yet. Before you go, we'll be more than happy to educate you on nature's energy currency that's in all living things like you!
We'll be going over the basics such as what ATP is made up of, what the cellular functions and roles are; we'll sprinkle in how ATP actively works inside plants, animals, microorganisms, and even during daily human activities. Lastly, we'll talk about how we use adenosine triphosphate outside of the realm of biology, so hold tight; it does get interesting!
We're going over everything you need to know in English, and we'll try to stay away from as much scientific jargon as possible—the keyword here is to "try"—because Wikipedia's article is packed with it. Believe us, we just checked 10 minutes ago.
So let's dive into some biology 101 concepts first, and then we'll show you how vital ATP is to life and its other beneficial uses.
All Aboard the Biomolecular Train!
Remember this mnemonic (nih-MAH-nik) phrase because we'll be referring to it later; it kind of sounds like a train leaving the station, well, sort of: "CHO, CHO, CHON, CHONP!"
To fully understand how critical ATP is for survival, you first need to know a little bit about cells. You see, cells are the literal building blocks to life. Cells and living organisms naturally produce substances called biomolecules to perform certain functions and are made up of them too.
Biomolecules are composed of monomers that connect to other monomers to form large complex polymers.
Think of monomers as Lego blocks and each Lego block (monomer) stacks on top of another Lego to form a complex chain or cellular structure (polymer).
There are four classes of biomolecules, and they can be broken down on a macro (large) and micro (tiny) level. And you see and eat most of these biomolecules in your life, and one of which you can't see nor realize you're eating it.
You have carbohydrates (e.g., bread), lipids (e.g., cheese), proteins (e.g., red meat), and lastly, you have nucleic acids (DNA and RNA)—the exception we were talking about because you can't see them, but you eat them, you just don't realize it.
At the very basic level, without going into extreme detail, biomolecules have their own monomers and polymers, or basic building blocks, to create each of these complex macromolecules.
Carbohydrates are made up of simple and complex sugars, and complex sugars are referred to as starches. Proteins are made of amino acids, and if you've ever seen an amino acid powder supplement with the label "BCAA" on it, just know it's a protein that has been separated and broken down.
Lipids are composed of fats and oils that also range from simple to complex structures and are so essential to life that they deserve their own blog post. Nucleic acids are made of monomers called nucleotides, which are sugar molecules built on a nitrogenous base attached to a phosphate group—it'll make sense later, promise.
But if you'd like, check out this very fun animated video by the Amoeba Sisters as they cover each building block of the four biomolecules with real-world examples as we transition into what their chemical structures are.
Remember that weird-sounding mnemonic train reference from earlier?
Well, carbohydrates and lipids are made up of carbon, hydrogen, oxygen (CHO); most proteins are made up of carbon, hydrogen, oxygen, and nitrogen (CHON); and nucleic acids are made up of carbon, hydrogen, oxygen, nitrogen, and phosphorous (CHONP).
And for a bonus! Bacteria and humans are made of carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur (CHONPS), plus some various elements from the periodic table of elements you might be familiar with.
Back to nucleic acids, so deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are a part of every living organism in all living cells. From a single-cell organism such as bacteria, viruses (minus retroviruses; RNA only), and archaea (oldest bacteria on Earth) all the way to multicellular mammals like you and me, plants, fungi, and protists (e.g., plankton).
DNA is like a computer programmer that writes all the genetic instructions for how an organism will develop, survive, and reproduce using genetic code in its cells, and then RNA is the translator who transcribes that code into proteins to accomplish those cellular functions. Where's ATP in all of this?
It's a part of the same nucleic acid group, all living things use ATP in some way or another, and it's made of similar building blocks found in DNA and RNA—ATP is a building block for RNA—but its purpose serves various functions outside the nucleus.
What Makes ATP, Adenosine Triphosphate?
ATP is a nucleotide derivative, yet it is chemically structured like DNA and RNA if you remember the mnemonic CHONP acronym. As a derivative, ATP has three parts that mirror its nucleotide counterparts, DNA and RNA.
It has a nitrogenous base called "adenine." Adenine is connected to a backbone of five-carbon sugar rings called "ribose sugar" to form "adenosine," and it has a phosphate group composed of "three phosphates" (triphosphate).
You can see how ATP gets its name, "adenosine triphosphate," and it has been given the reputation of being an energy currency of the cell.
You've probably seen it in your old biology books drawn as a lightning bolt or a tiny blast of energy occurring inside a diagram of a cell to show cell processes in action. While it's true that ATP is a source of energy, its illustrative depiction isn't to be taken literally, but how it actively plays a role in cellular functions should be.
Alright, it's about to get increasingly sciency and technical so bear with us, please.
Naturally, ATP is unstable, and it's bonded by three phosphate molecules. The link between the three phosphates is where the available energy is contained. What causes the release of chemical energy is the breaking of the phosphate tail and it's always the last phosphate molecule that gets the worst end of the deal.
This burst of energy mostly happens during hydrolysis when ATP has been added to water which causes a reaction. As the last phosphate on the tail breaks, ATP then turns into adenosine diphosphate or ADP for short.
Another instance where ATP energy is created is during cellular homeostasis with the myokinase enzyme's help. This is when two ADP molecules collide (interconversion) to form one ATP and one adenosine monophosphate molecule (AMP). AMP is added to ADP to create more ATP and the main role of myokinase is to keep cellular energy levels balanced (homeostasis).
Fun fact, myokinase reactions occur in our muscles when we do high-intensity exercises, and it's a signal to the cell for energetic stress. Not the same stress you'd feel because you didn't study before an exam, but a good stress, signaling our muscles to work harder by creating ATP energy.
As cells are continuously breaking down ATP for energy, all is not lost for ATP, and it will be regenerated during a specific process that creates an abundance of it, but we'll get into that much later.
So, now that you're familiar with what adenosine triphosphate is, let's show you how important it is for cells and all living organisms. The fun part is that ATP doesn't just have one job, and it wears many hats and plays many roles in life.
What Does ATP Do?
More like what doesn't it do. All living organisms' cells use ATP one way or another. Generally, cells need chemical energy to be released for many vital processes, and this is where ATP gets to shine!
For example, one of ATP's many cellular functions is active transport during the cellular diffusion process. ATP helps cells move molecules that exist in lower concentrations to where there are higher concentrations of molecules so that the total concentration of molecules becomes equal.
ATP moves macromolecules, such as protein and lipid molecules, during active transport. ATP moves them in and out of cellular membranes (cell wall) by using its energy to help push them through a resistant cell wall because they alone don't have enough energy to do it themselves because that would be passive transport.
Another major life-sustaining role of ATP is to drive metabolic reactions within the cells of organisms to convert nutrients into energy (ATP) for cell growth and repair (cellular division), digestion, homeostasis (e.g., sweating), fermentation, photosynthesis, and so much more!
You know how some people say, "Oh, I have a fast metabolism," while others may say they have a slow one. These metabolic reactions can tie into how some people metabolize foods faster than others and even sweat more than others too.
There are over 5000 biochemical reactions that are occurring in animals, humans, plants and even microbes through a series of organized reactions. You can think of it as a pathway of multiple processes that are taking one chemical result and turning it into another chemical result after the other, and with the help of enzymes (proteins), these reactions are sped up to complete a chain of reactions.
So, where does ATP fit in all this? Keep reading below because it deserves its own section.
Cellular Respiration Explained
The cells of organisms, whether it's a eukaryote cell (animals, plants, insects, fungi, protists) or prokaryote cell (bacteria and archaea), have their own way of "sweating" out waste after completing a series of complex metabolic reactions to create ATP.
For example, glucose from carbohydrates and many other molecules such as protein and lipids from the foods we eat are broken down to convert biochemical energy into ATP, and as a result, release waste products. The entire series of chemical reactions is called cellular respiration.
During cellular respiration, a series of catabolic reactions are occurring where macromolecules are broken down into smaller molecules (requiring ATP) and the final result after a series of reactions, is more ATP energy (heat) being released.
Enzymes play a huge role during this process because a large number of them are needed to perform each reaction. Every time energy is converted into ATP during this process, some heat is lost each time from the sugar (glucose) molecule being broken down and this happens with other types of macromolecules.
That's why you'll often see runners load up on carbs (sugar) the night before a marathon so that they'll have enough energy for the big race.
There's another type of cellular respiration process that doesn't involve food at all but actually just air (oxygen) to create ATP. It's called aerobic cellular respiration, and the process of how it's carried out differs for eukaryotic and prokaryotic cells, and it's different for plants compared to animals as well.
Don't hold your breath as we get into it, but aerobic cellular respiration has several parts to it. The reason why breathing in air is so vital is not only just to live, but it's an essential source of energy where ATP is created.
This process happens all the time for animals, humans, and plants in the cell's mitochondria, and even some prokaryotic organisms have their own version of aerobic respiration even though their cells don't have mitochondria. However, most bacteria perform the opposite of aerobic respiration and perform anaerobic respiration processes without the need for oxygen molecules. So take a deep breath as we summarize other ways ATP is made.
The Three Stages of Aerobic and Anaerobic Cellular Respiration
Some Parts of the processes involve oxygen and it's why we need to breathe in air to survive. Breathing in oxygen is an important part of producing ATP and it's how we give fuel for our cells to produce energy. The end byproduct of cellular respiration when we breathe out air is carbon dioxide. This is the waste produced by cells that have burned up the sugars and fatty acids in our cells.
But what's happening when we breathe? Turns out, breathing in air is a little more complex than you think. And for plants, the process is similar as it relates to aerobic cellular respiration, but the chemical formula is reversed.
Now, where do most of these reactions occur to create ATP? In the cell's powerhouse AKA, the mighty mitochondria of course!
ATP is produced during each of the three steps of cellular respiration, and the final result of how much ATP is produced can range. It's not uncommon for you to see this number fluctuate in different biology books or online sources.
The overall formula for aerobic cellular respiration is written out like this and the reactants or inputs are on the left side, and on the right side of the arrow is the product or output (final result):
C6H12O6 (glucose) + 6 O2 (oxygen) → 6 CO2 (carbon dioxide) + 6 H2O (water) + 28–38 ATP is more or less produced; this is highly debated, and some editions of school biology books have it listed with approximate numbers such as "36" or "32," so it's better to list a range instead.
For plants, as we said earlier, it's a similar formula, so here's what photosynthesis looks like:
6 CO2 + 6 H2O →(light)→ C6H12O6 + 6 O2.
Plants perform cellular respiration and photosynthesis to produce glucose and break it down, and cellular respiration for organisms that aren't plants will break down glucose for energy.
Plants are autotrophs and can make their own food for energy but unfortunately for us, we have to find food to eat—or just order from UberEats—so we can break down food (e.g., glucose) for ATP energy, which brings us to phase one out of three: "Glycolysis."
What is Glycolysis?
What is about to occur in each of these three phases is a complex series of reactions that create products, and the products of each reaction will then get turned into substrates, which is jargon for an end result that becomes an input.
So, it's a cycle of inputs and outputs and those outputs become inputs and it's super complex, so let's try to keep it simple.
In this step of cellular respiration, oxygen isn't needed, so the first stage in glycolysis is anaerobic and it all starts in the cell's cytoplasm. During glycolysis, the glucose sugar molecule (C6H12O6) from our formula gets broken down and converted into two molecules called pyruvate (C3H4O3).
Pyruvate (pyruvic acid) is a more usable molecule that helps get the process of glycolysis going. At the start of glycolysis, a little bit of ATP energy is used up to form pyruvate, two ATP molecules are generated as well, and two NADH coenzymes (nicotinamide adenine dinucleotide + hydrogen), which have the ability to transfer electrons way later on in this process to create even more ATP. This process repeats itself for each glucose molecule.
But before we get into phase two, to create more ATP, there's a step in the middle, so now we're about to move into phase one and a half technically.
Remember when we talked about active transport?
In this intermediary step, two pyruvate molecules are actively transported into the innermost part of mighty mitochondria. They have now entered the mitochondrial matrix—kind of like the movie—as Morpheus says, "What if I told you the oxidation of pyruvate happens in the mitochondrial matrix?"
All jokes aside, it's true, two pyruvate molecules get oxidized, carbon dioxide is released and gets converted into two acetyl CoA molecules, which are necessary for phase two. During this oxidation process, two NADH molecules are made and will be used later in the cellular respiration process.
Now we enter phase two! But we're still in the mitochondrial matrix, and this is where things get "cyclical" or never-ending and the final product is a small amount of ATP.
Enter the Krebs Cycle
The Krebs cycle is also known as the citric acid cycle. Pyruvate has just been converted into acetyl CoA, and now it's entering an aerobic process. Not every part of the cycle requires oxygen, but some will require it to keep the Krebs cycle going.
The Krebs cycle is pretty complex to explain and doesn't produce that much ATP, but to summarize, there are eight steps that occur in a closed series or loop of processes where redox, dehydration, hydration, and decarboxylation reactions occur.
The decarboxylation reaction produces two carbon dioxide molecules, an ATP or GTP (guanosine 5'-triphosphate) molecule, and reduced forms of NADH and FADH2 (flavin adenine dinucleotide) or QH2 (ubiquinol).
FADH2 is a coenzyme that will be used later in this process just like NADH in the assistance of transferring electrons.
Now since each glucose molecule gets broken down into two pyruvate molecules, those two pyruvate molecules get converted into two acetyl CoA molecules and it then gets converted into oxaloacetate. This oxaloacetate molecule is the final product out of the eight central molecules that are produced to keeps this loop going.
For each molecule of glucose, the Krebs cycle has to loop twice; therefore, at the end of every second cycle, the end results are two ATP molecules, six NADH and two FADH2 (proteins) or QH2 (lipids; lipolysis) molecules, and lastly, four CO2 molecules are given off.
We are now entering phase three where the maximum net yield of ATP is produced, and it's again, very complex to go into detail. We'll "try" to make it easy to digest and we are now leaving the mitochondrial matrix and moving into the inner mitochondrial membrane.
Ride the Electron Transport Chain With Chemiosmosis
The sole purpose of the electron transport chain is to create a proton gradient to maximize ATP production. This phase is an aerobic process so oxygen will be required.
Here's a call back to two things, NADH and FADH2 are utilized in this process to create ATP and the real contributor here is NADH and not so much so FADH2 because it has lower electron energy levels.
Secondly, remember ATP losing a phosphate, which then turns into ADP? That happens here too.
NADH and FADH2 are transferred through protein complexes and electron carriers, so this is the electron transport chain super simplified. It's these two types of molecules that carry an electrical charge traveling from the mitochondrial matrix through an inner mitochondrial membrane.
Both of these molecules are oxidized, which means they lose an electron in the hydrogen molecule (the "H" in their names). When they lose their electrons, for example, NADH will turn into NAD+ and that goes back into the Krebs cycle, the electrons will then be used to create a proton gradient as protons are pumped across to the intermembrane space of a cell (chemiosmosis).
Now, imagine this in mass and imagine all these protons being pumped out into this intermembrane space to generate an electrical charge and chemical gradient too.
Active transport kicks in again during this stage because hydrogen ions (H+) don't have the easiest time traveling directly through membranes. They need a vessel that can help take them across and out of the cell's membrane.
Here's where an amazing enzyme called "ATP synthase" helps these protons (H+) travel through and this is where ATP is made in bulk. What ATP synthase does, is that it adds a phosphate to ADP to create ATP, so think of it as a turbine that looks like an upside-down mushroom?
Back to chemiosmosis!
Protons are traveling down an electrochemical gradient and passing through ATP synthase where they figuratively power the turbine to make ATP.
Outside of the membrane, oxygen accepts the electrons and combines with two hydrogens to create—you guessed it—water! Which is the end product of our equation (6 H2O) and also a range of 28–38 ATP molecules are produced if you count the total produced in each of the three steps.
This was one very exhaustive way in how ATP can be produced. There's another process for cells that don't do aerobic cellular respiration and can only do anaerobic respiration if there's no oxygen present. This process is called fermentation and it's not the best at creating ATP.
The Wonders of Fermentation
Fermentation and its amazing ability to produce wine and help bread rise because of yeast—a productive fungus—is something we are all aware of. Maybe fermentation isn't so obvious when you feel that pain you get after a workout and that's because lactic acid is forming in your muscles.
But, did you know that some species of bacteria and archaea organisms use fermentation to create ATP energy as well? Some organisms have evolved to perform glycolysis only and some use sulfate as an electron acceptor during the electron transport chain process in cellular respiration.
Bacteria use the same processes used to generate ATP energy that we went over in the three phases of aerobic cellular respiration.
The prokaryotic organisms (some bacteria and archaea) that handle a lack of oxygen and function without it through fermentation need to use anaerobic and aerobic cellular respiration processes to keep their own way of glycolysis going to produce ATP.
So how do they produce energy when there's no oxygen? Well, remember that in glycolysis, glucose is broken down into pyruvate, and as a result, two ATP molecules are produced and two NADH molecules; these are the electron-carrying molecules that get made after NAD+ gets reduced, meaning NADH gains an electron.
Normally, NADH would deliver electrons in the electron transport chain if this were an aerobic cellular respiration process, but not so fast! During fermentation, what's done to create more ATP is an addition of a few steps during the glycolysis stage to create more NAD+.
What's key here to making more and more ATP, although it's not a lot of ATP, is the recycling of NADH to generate NAD+ so that NAD+ goes back into the Krebs cycle inside the cytoplasm of prokaryotes. Fermentation produces very little ATP, and it makes you appreciate the reason why living organisms need oxygen to breathe because aerobic cellular respiration has the highest yield of ATP.
Other uses of fermentation that do not make ATP won't be discussed here because this post is all about ATP. Let's talk about the ways ATP is used outside the realm of biology.
ATP in Action
You've probably seen ATP in action if you've ever seen a firefly glow. What's happening is that oxygen, luciferin, and luciferase enzymes react with ATP to produce a bright bioluminescent light.
And you can see this happening with other organisms such as some species of animals that dwell in the darkest depths of the ocean, but there are additional molecules at play such as potassium and sodium, etc.
So, by now, you know that ATP is in all living things and this applies to mold and bacteria too. It's even present from residues leftover from some foods and other miscellaneous organic material.
But did you know that ATP can determine the level of cleanliness on a surface? A surface may look clean but that doesn't mean it is. One of the best ways to verify if a surface is clean is through ATP testing.
So how do we use ATP at Germinator? We use it before and after our services to measure hygiene using a device called a luminometer. Using a special swab, we are able to swab a surface a few times to pick up any matter that may exist.
We take that swab and place it inside its capsule, where it is then snapped so that the luciferase enzyme can activate and catalyze (speed up) a reaction to break the phosphate tail of ATP to give off energy (light).
After the swab has been snapped and placed inside the luminometer, our technicians will wait 15 seconds for a numerical readout of how much organic matter had been left on a surface.
The unit of measurement is in relative light units (RLUs) and we use a grading scale to determine your level of cleanliness. The grading scale goes as follows: 0–20 you can literally eat off a surface; it's that clean, 20–50 is an ideal level of cleanliness, 50–100 is an acceptable level, 100–120 is an area of caution, and anything over 120 needs sanitizing and disinfecting.
The reason why contaminated surfaces need to be sanitized and disinfected is that the possibility for the growth of mold or bacteria can be likely and they'll have the nutrients they need to start growing if it's left untreated. That's why routine cleaning, sanitizing and disinfecting all go hand in hand to create hygienic and protected spaces.
Here at Germinator, we use the most advanced antimicrobial science and our own patent-pending methodology to not only sanitize and disinfect, but provide proven, next-level protection to safely kill viruses, bacteria, and other contaminants.
Learn how we create a more livable, touchable Germinator Safe Zone as we wrap up today's lesson on "What is Adenosine Triphosphate?"
Class is Dismissed!
Without ATP, we'd literally die, not even kidding.
You've learned how vital it is for all living organisms that breathe in air to break down glucose and other macromolecules into energy to keep the processes of a cell going and alive. Even those organisms that don't use oxygen in their anaerobic cellular respiration process find one way or another to produce energy.
The foods we eat are major contributors to how we produce ATP energy to fuel activities like exercise or just plain survival. There was a lot of science, a pinch of math during those formulas and a ton of biochemistry/biology involved in this post. But you got to see how beneficial ATP is to our life and even seen how useful ATP is outside the realm of biology—technically it's biotechnology.
We use ATP testing to ensure and verify that you're in a Germinator made Safe Zone and we use it to educate you on better hygiene practices because we just want you to feel safe. It's the reason we got into this business back in 2015.
Every day, we go into day cares, fire stations, office buildings, restaurants, shopping malls, and homes to provide the most advanced sanitizing and disinfecting service that the industry can deliver.
Why do we do it?
Because we believe that everyone has a right to better well-being and to feel safe in the spaces they live, work, and play. We want people to feel comfortable, and most importantly, protected—no matter where they are.