You have most likely heard of ATP in your high school biology class. As a refresher, ATP stands for adenosine triphosphate, and it acts as the source of energy for many chemical reactions and cellular processes in the human body. Without ATP we wouldn’t have the fuel to complete the day-to-day bodily processes that keep us alive!
With such a vital molecule, ATP seemingly flies under the radar when talking about molecules that convey energy. Many companies instead like to focus on molecules such as caffeine to boost perceived energy levels.
While caffeine can trick your mind into being more awake and alert, it does nothing in terms of providing your body with real energy. A great way to think about the two in terms of the level of importance is to note that you can live without caffeine, but you couldn’t exist without ATP.
ATP is a synthesized molecule within the body. Its synthesis occurs at a cellular level in the structure known as the mitochondria. Each mitochondrion is like a small ATP-producing machine.
Below is a closer look at everything you need to know about ATP including what it is, where it is made, and how it is made.
What Is ATP?
ATP, also known as adenosine triphosphate, is an energy-rich molecule that the body utilizes to catalyze otherwise nonspontaneous reactions. ATP holds its energy between the second and third phosphate groups. When the third phosphate is cleaved it results in the release of energy that can then be harnessed by a number of different reactions which allow them to occur.
ATP is considered a nucleotide, which is one of the four main macromolecules found within the human body. Nucleotides make up the structure and code of DNA but also play a role in usable forms of cellular energy. In addition to adenosine triphosphate, the molecule guanosine triphosphate exists as another energy-dense nucleotide molecule for certain reactions.
As the name of ATP implies, there are three phosphate groups and because of this, ATP has two other forms. Below is a closer look at the forms of ATP and what they do for the body.
AMP is adenosine monophosphate and it is the least energetic molecule of all forms of ATP. AMP is utilized as a monomer for RNA, but AMP can also act as a signaling pathway for certain reactions. When you think about it, AMP represents a good molecule to look out for since AMP is the least energetic and most energetically reduced form of ATP. Specifically, a form of AMP known as cyclic AMP is a potent regulator for sugar, lipid, and glycogen metabolism.
The main purpose of ADP is to act as an intermediate to ATP. ADP has an additional phosphate over AMP and in certain instances, the second phosphate can be utilized as a source of energy to conduct reactions.
ATP is the coveted energy currency within the cell. ATP has three phosphate groups and the bond between the second and third phosphate is quite energetically high and is why ATP is utilized in so many reactions.
Where Is ATP Made?
So, you know ADP is the precursor to ATP, but where exactly is ATP made? ATP is mainly made by a cellular structure known as the mitochondria. The mitochondria are a unique structure within the cell that is believed to at one point in evolutionary history been separate bacteria.
The endosymbiont theory suggests that a cell engulfed the bacteria, and rather than breaking it down, the smaller cell posed a benefit by which the pre-mitochondria cell was able to survive. This theory is strongly supported by a number of different factors that are still seen to this day. This includes the fact that the mitochondria divide independently of the cell and that they contain their own set of DNA.
The structure of the mitochondria is unique as it has a double membrane with an intervening space between them. The mitochondria also have CoQ10 within their membranes, which is a lipid-soluble molecule that can act as an antioxidant.
The mitochondria are constantly pumping out ATP, and in the process, are creating reactive oxygen species, which could cause oxidative damage to the membrane if CoQ10 were not present. Unfortunately, CoQ10 levels have the possibility to decline, and this is where MitoQ comes in.
MitoQ is a modified CoQ10 supplement that is readily absorbed and integrated into the highly selective mitochondrial membrane to help fight back against oxidative stress.
How Is ATP Made?
The majority of the ATP in the cell is made in a process known as cellular respiration. Cellular respiration consists of the conversion of glucose and oxygen to ATP, water, and carbon dioxide. Cellular respiration is a complex multi-step process that can be broken down into three main stages. This includes glycolysis, the Krebs cycle, and the electron transport chain.
Glycolysis is where cellular respiration begins and it is also the first point at which ATP is produced. In addition to producing ATP, glycolysis also yields NADH, which is a molecule that can be utilized in the electron transport chain to yield more ATP.
Simple sugars like glucose are broken down during glycolysis into three-carbon molecules known as pyruvate. Glycolysis occurs outside of the mitochondria and represents the basis of anaerobic respiration since none of the steps thus far have required oxygen.
The Krebs cycle, also known as the TCA cycle, begins with the conversion of pyruvate to acetyl-CoA. Once converted to acetyl-CoA, the molecule can then go into the TCA cycle where carbons are rearranged and slowly removed in the form of carbon dioxide. Each loss of carbon releases energy and the Krebs cycle harnesses that energy in the form of ATP, NADH, and FADH.
Electron Transport Chain
The electron transport chain is the last step in the process of cellular respiration. Looking at ATP synthesis thus far, only four ATP have been produced. The electron transport chain is truly where the mitochondria are able to cash in on carbohydrate metabolism for ATP.
The NADH and FADH2 synthesized in the other stages of cellular respiration are what drive this part of cellular respiration. Rather than reactions simply occurring, this stage involves the interaction with the integral membrane proteins within the mitochondria.
There are four separate complexes and one protein called ATP synthase which turns ADP into ATP. ATP synthase is fueled by a high proton concentration in the intermembrane space which comes from the four complexes.
The electron transport chain starts off with the oxidation of NADH to NAD+ with complex 1. This oxidation transfers an electron to the complex which in turn allows the surface protein to pump a proton into the intermembrane space.
The next to occur is that FADH2 can interact with complex 2. Rather than providing more protons to the intermembrane space, the oxidation of FADH2 results in the transfer of electrons, but also the subsequent shuttling of those electrons with CoQ10 to complex 3. From Complex 3, cytochrome C helps to continue the journey of the electron to complex 4, where the journey of the electron ends with oxygen being the final electron acceptor. The movement across complexes 3 and 4 yields more protons in the intermembrane space.
After all of the electron moving and proton pumping the intermembrane space contains a high concentration of protons. ATP synthase is a membrane-bound protein that kind of acts as a bleed-off valve. As it releases some of the protons it simultaneously takes ADP and adds a phosphate to yield ATP.
As long as cellular respiration and the electron transport chain continue to create the intermembrane proton gradient the ATP synthase molecule can keep turning out ATP.
One potential issue with the mitochondria is that they can be susceptible to membrane damage due to reactive oxygen species that are reproduced as a result of natural energy production. If the membrane is damaged due to oxidation, it could lead to a leaky inter-membrane which would then decrease the ability of ATP synthase to work at its best.
MitoQ is a specially formulated version of CoQ10 that has the ability to support and provide antioxidant relief to the mitochondrial membrane and help to reduce the chances of oxidative membrane damage.
In summary, ATP is the energy currency of the cell and is made within the cellular structure known as the mitochondria. The process of converting ADP to ATP is long, but with this convoluted mechanism, the cell is able to turn out ATP on a consistent basis.