Adenosine triphosphate

Adenosine 5'-triphosphate

Chemical name	[[[5-(6-aminopurin-9-yl)-3,4-dihydroxy-oxolan-2-yl] methoxy-hydroxy-phosphoryl] oxy-hydroxy-phosphoryl] oxyphosphonic acid
Abbreviations	ATP
Chemical formula	C₁₀H₁₆N₅O₁₃P₃
Molecular mass	507.181 g mol^-1
Melting point	? °C
Density	? g/cm³
pK_a	?
CAS number	56-65-5
EINECS	200-283-2
PubChem	5957

Adenosine triphosphate (ATP) is the chemical compound known in biochemistry as the "molecular currency" of intracellular energy transfer; that is, ATP is able to store and transport chemical energy within cells. All cells&mdashprokaryote, animal, and plant&mdashuse ATP as the principal energy-carrying molecule and as the main energy source for driving energy-requiring reactions (endergonic); as such, ATP has been referred to as "life's energy currency" (Luria, Gould and Singer 1981).

In short, living cells require energy to survive and function, and most of this energy comes either via radiant energy from sunlight or from chemical energy tied up in interatomic bonds of nutrient molecules. When nutrient molecules coming from carbohydrates, fats, and proteins are oxidized by cells, a portion of the free energy released can be captured in the chemical bonds of ATP. ATP allows the storing of energy in cells as chemical potential and the circulation and use of this energy by the cell.

In addition to its energy-related function, ATP also plays an important role in the synthesis of nucleic acids. In signal transduction pathways, ATP is used to provide the phosphate for the protein-kinase reactions.

The ubiqutous presence of ATP in the cells of all living organisms indicates that it must have appeared early in the history of cellular life. The intricacy of how ATP is used by the body in various metabolic pathways, and its fundamental importance to living systems, reveals the complex interaction between parts of living systems.

Chemical properties

ATP consists of adenosine and three phosphate groups(triphosphate). The phosphoryl groups, starting with that on AMP, are referred to as the alpha (α), beta (β), and gamma (γ) phosphates. ATP is extremely rich in chemical energy, in particular between the second and third phosphate groups. The net change in energy of the decomposition of ATP into ADP and an inorganic phosphate is -12 kCal / mole in vivo, or inside of a living cell, and -7.3 kCal / mole in vitro, or in laboratory conditions. This massive release in energy makes the decomposition of ATP extremely exergonic, and hence useful as a means for chemically storing energy.

Synthesis

Space filling image of ATP

ATP can be produced by various cellular processes: Under aerobic conditions, the synthesis occurs in mitochondria during the oxidative phosphorylation and is catalyzed by ATP synthase; to a lesser degree, under anaerobic conditions, this is done through substrate phosphorylation catalyzed by two enzymes: PGK and Pyruvate kinase.

ATP is also synthesized through several so-called "replenishment" reactions catalyzed by the enzyme families of NDKs (Nucleoside diphosphate kinases), which use other nucleoside triphosphates as a high-energy phosphate donor, and the ATP:guanido-phosphotransferase family, which uses creatine.

ADP + GTP

\to

ATP + GDP

In plants, ATP is synthesized in chloroplasts by photosynthesis during the light reactions of photosynthesis. However, this ATP is then used to power the Calvin cycle step of photosynthesis and so photosynthesis does not result in an overall production of ATP.

Adenosine monophosphate
AMP

Adenosine diphosphate
ADP

Adenosine triphosphate
ATP

The main fuels for ATP synthesis are Glc and FAs. First, Glc is broken down into pyruvate in the cytosol. Two molecules of ATP are generated for each molecule of Glc. The terminal stages of ATP synthesis are carried out in the mitochondrion and can generate up to 36 ATP, which is 40% energy efficiency.

Function

ATP energy is released when hydrolysis of the phosphate-phosphate bonds is carried out. This energy can be used by a variety of enzymes, motor proteins, and transport proteins to carry out the work of the cell. Also, the hydrolysis yields free inorganic P_i and ADP, which can be broken down further to another P_i and AMP. ATP can also be broken down to AMP directly, with the formation of PP_i. This last reaction has the advantage of being an effectively irreversible process in aqueous solution.

ATP in the human body

The total quantity of ATP in the human body is about 0.1 mole. The energy used by human cells requires the hydrolysis of 200 to 300 moles of ATP daily. This means that each ATP molecule is recycled 2000 to 3000 times during a single day. ATP cannot be stored, hence its consumption must closely follow its synthesis. On a per-hour basis, 1 kilogram of ATP is created, processed and then recycled in the body.

Other uses

There is talk of using ATP as a power source for nanotechnology and implants. Artificial pacemakers could become independent of batteries. ATP is also present as a neurotransmitter independent from its energy-containing function. Receptors that utilise ATP as their ligand are known as purinoceptors.

External link

ATP and biological energy

Nucleic acids edit
Nucleobases: Adenine - Thymine - Uracil - Guanine - Cytosine - Purine - Pyrimidine
Nucleosides: Adenosine - Uridine - Guanosine - Cytidine - Deoxyadenosine - Thymidine - Deoxyguanosine - Deoxycytidine
Nucleotides: AMP - UMP - GMP - CMP - ADP - UDP - GDP - CDP - ATP - UTP - GTP - CTP - cAMP - cGMP
Deoxynucleotides: dAMP - dTMP - dUMP - dGMP - dCMP - dADP - dTDP - dUDP - dGDP - dCDP - dATP - dTTP - dUTP - dGTP - dCTP
Nucleic acids: DNA - RNA - LNA - PNA - mRNA - ncRNA - miRNA - rRNA - siRNA - tRNA - mtDNA - Oligonucleotide

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