ATP - a short overview
ATP, short for adenosine triphosphate, is THE energy carrier of our body. Each muscle cell completely uses up its stored ATP every minute during regular activity. This corresponds to about 10 million ATP molecules per second per muscle cell. During maximum contraction of the muscle cell, the stored ATP depletes completely within 2-3 seconds.
This shows how relevant ATP is, among other things, for muscles during movement, heart muscles, but also supporting muscles. ATP is the universal energy carrier of our organism. It is found in every cell for energy supply, be that a nerve cell, muscle cell or supporting cell (connective tissue cells, cartilage, ...).
But how is this ATP produced? And what is it exactly?
What is ATP?
ATP consists of several parts: It has a sugar residue, ribose, an adenine residue and 3 phosphate groups. Of course, this is a bit complicated.
Adenine is a base. It is also found, for example, in our DNA, which you might remember from biology class in school.
Ribose is the central part of the molecule and it is mainly structurally important.
The phosphate groups are the actual energy carriers or energy stores. When ATP is formed, the energy is packed into the phosphate groups, so to speak, because when one of them is split off from the molecule, a relatively large amount of energy is released, which can then be used for other reactions in the body.
ATP - the production site
If ATP is constantly available in every cell in the millions, then the production site of the cell cannot deviate far from it.
ATP is produced in mitochondria, the power plants of our cells. Up to 5,000 mitochondria are found in a single cell.
The basic structure of mitochondria is particularly interesting. It looks as if, developmentally, they were once independent cells a long time ago that entered into a symbiotic relationship with our former cell. By immigrating into our cell, mitochondria typically have two membranes, the demarcation to the external space. One of them resembles our cell membrane, but the inner one resembles the membrane of a single-celled organism.
The inner membrane is involved in energy production and is folded inward to increase the production surface area. Here sits a special enzyme, ATP synthase, which performs the final step of energy production.
ATP production - the respiratory chain
The energy supply of the mitochondria is a very complex process. This is called the respiratory chain. This also has something to do with respiration, because oxygen is mostly used in the form of O2.
Equally important is a substance that is consumed during energy production. The standard substance used here is glucose. Energy production generally works by consuming fats, proteins, and carbohydrates. The energy obtained in this process is stored temporarily and then used in the respiratory chain. Here, this energy is ultimately transferred to ATP through a wide variety of reactions.
In addition, we have some cofactors such as coenzyme Q10. Coenzyme Q10 is used for electron transfer, which is crucial in the respiratory chain.
How much energy does ATP have?
One molecule of ATP releases either 32.3 kJ or 64.6 kJ of energy. This comes from the fact that either one phosphate group (32.3 kJ) or two phosphate groups (64.6 kJ) of the adenosine triphosphate can be split off. Depending on this, we obtain ADP (adenosine diphosphate) or AMP (adenosine monophosphate). Energy is released during the cleavage because phosphate groups are very energetic and charged.
64 kJ may seem low at first for this amount, converted it would be about 3g of chocolate, however this amount is just right for the body to perform other reactions. The body has thus greatly compressed the energy of the original substances (carbohydrates, fatty acids, proteins).
Oxidation in the respiratory chain - antioxidants
Earlier we mentioned that oxygen is also involved in the respiratory chain. What does this mean?
The respiratory chain produces, among other things, oxidized oxygen molecules. These are very aggressive structures, because they are constantly looking for a binding partner and thus disrupt existing proteins, enzymes and molecules. When there is an excess of these radicals, oxidative stress can result. A healthy mitochondrion can neutralize these radicals with antioxidants stored in the membranes. As a result, the mitochondrion and, under certain circumstances, the entire cell are not subjected to a higher level of stress.
Excessive radical attack mainly increases the risk of mitochondrial DNA (mtDNA) damage. In addition, the radicals inhibit enzymes of the respiratory chain and damage the inner mitochondrial membrane. Mitochondrial substances that are toxic to the cell may cause the cell to die. The mitochondrion or the cell can therefore also no longer produce ATP.
Protection against the possible negative effects of the respiratory chain is therefore essential. The antioxidant content of the mitochondrion should therefore always be at a constant level.
Mechanism of energy release
Now ATP has been synthesized. But how can energy release occur? Earlier we briefly discussed the influence of the three phosphate groups.
As a universal energy carrier, one or the other may not yet have an optimal idea of the function of ATP on individual processes.
In the case of muscles, ATP is needed for contraction. For example, during a sprint, which is supposed to represent a full contraction of the muscles, the first 2-3 seconds are made possible by ATP storage alone. After that, for the next few seconds (10 seconds total), ADP is regenerated into ATP in a rapid manner with the help of creatine monophosphate by transferring the phosphate group. After that, more elaborate processes take hold, as creatine storage is also limited.
And don't forget: In principle, the heart is also a large muscle.
The nerve cell also contains a large number of mitochondria and thus a lot of ATP. Nerve cells use their projections to transmit information to the next cell. ATP is also needed for this and other processes.
The surface area of the intestine is increased for improved nutrient absorption by elevations and depressions of the inner surface. This construct is renewed again and again every few days. In the process, the deepest cells divide and migrate upward. Of course, ATP is also involved in the process of cell division and tissue renewal. Mitochondrial activity, and thus ATP production, is crucial for cell renewal to proceed smoothly. In addition, the intestine, just like the nerve cell, contains ATP-dependent pumps that transport substances out of the cell or into the cell only when ATP is consumed.
As you can see, the functions of ATP in the body are broad, here you can see only a few points. ATP is a very important molecule, in the body it is like money on our planet, the commodity that is relevant to every individual.
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