What is adenosine triphosphate?
Adenosine triphosphate (ATP) is a mononucleotide of adenine with three phosphate groups, each linked by an anhydride bond. ATP is the central molecule for the transmission of energy in the organism.
The energy is mainly bound in the anhydride bond of the beta-phosphate moiety to the gamma-phosphate moiety. If a phosphate residue is removed with the formation of adenosine diphosphate, energy is released. This energy is then used for energy consuming processes. As a nucleotide ATP consists of the purine base adenine, the sugar ribose and three phosphate residues. There is a glycosidic bond between adenine and ribose. Furthermore, the alpha-phosphate moiety is linked to the ribose by an ester linkage.
There is an anhydride bond between alpha-beta and gamma-phosphate. After removal of two phosphates, the nucleotide adenosine monophosphate (AMP) is formed. This molecule is an important building block of RNA.
Function, effect & tasks
Adenosine triphosphate exerts many functions in the organism. Its most important function is the storage and transmission of energy. All processes in the body are associated with energy transfers and energy transformations. So the organism must perform chemical, osmotic or mechanical work. ATP provides energy quickly for all these processes.
ATP is a short-term energy store, which is used up quickly and therefore has to be synthesized again and again. Most of the energy-consuming processes are transport processes within the cell and out of the cell. Biomolecules are transported to the sites of their reaction and conversion. Anabolic events such as protein synthesis or the formation of body fat also require ATP as an energy transferring agent. Molecule transports through the cell membrane or membranes of various cell organelles are also energy dependent.
Furthermore, the mechanical energy for the muscle contractions can only be provided by the action of ATP from energy-providing processes. In addition to its function as an energy carrier, ATP is also an important signaling molecule. It acts as cosubstrate for the so-called kinases. Kinases are enzymes that transfer phosphate groups to other molecules. These are mainly protein kinases that influence their activity through the phosphorylation of various enzymes. Extracellularly, ATP is an agonist of receptors of cells of the peripheral and central nervous system.
Thus it participates in the regulation of the blood circulation and the triggering of inflammatory reactions. In nerve tissue injuries, it is increasingly released to mediate the increased formation of astrocytes and neurons.
Education, occurrence, properties & optimal values
Adenosine triphosphate is only a short-term energy storage and is consumed in energy-consuming processes within a few seconds. Therefore, its constant regeneration is a vital task. The molecule plays such a central role that ATP with a mass of half the body weight is produced within a day. Adenosine diphosphate is transformed into adenosine triphosphate by an additional bond with phosphate under energy consumption, which immediately returns energy with elimination of the phosphate by re-conversion into ADP.
For the regeneration of ATP two different reaction principles are available. One principle is substrate chain phosphorylation. In this reaction, an energy-providing process transfers a phosphate moiety directly to an intermediate molecule, which is immediately passed on to ADP to form ATP. A second reaction principle is part of the respiratory chain as electron transport phosphorylation. This reaction occurs only in the mitochondria. As part of this process, an electrical potential is built up through the membrane through various proton-transporting reactions.
Due to the backflow of the protons, energy release leads to the formation of ATP from ADP. This reaction is catalyzed by the enzyme ATP synthetase. Overall, these regeneration processes are still too slow for some requirements. Thus, in muscle contraction, all supplies of ATP are consumed after two to three seconds. For this, energy-rich creatine phosphate is available in muscle cells, which immediately provides its phosphate for the formation of ATP from ADP. This supply is now exhausted after six to ten seconds. Thereafter, the general regeneration processes have to come to fruition again. However, the effect of creatine phosphate makes it possible to expand muscle training without premature fatigue.
Diseases & Disorders
If too little adenosine triphosphate is produced, exhaustion occurs. ATP is mainly synthesized in the mitochondria via electron transport phosphorylation. Mitochondrial function disorders also reduce the production of ATP.
Studies have shown that patients with a chronic fatigue syndrome (CFS) had a decreased ATP concentration. This decreased production of ATP always correlated with disorders in the mitochondria (mitochondriopathies). Causes of mitochondrial disorders included cellular hypoxia, EBV infections, fibromyalgia, or chronic degenerative inflammatory processes. There are both genetic and acquired mitochondrial disorders. Thus, about 150 different diseases have been described which lead to mitochondriopathy.
These include diabetes mellitus, allergies, autoimmune diseases, dementia, chronic inflammation or immunodeficiency disorders. The states of exhaustion associated with these diseases are caused by lower energy supply due to the reduced production of ATP. As a result, disorders of the mitochondrial function can lead to multi-organ diseases.