Cookies help us deliver our services. By using our services, you agree to our use of cookies. More information

Adenine nucleotides

From Bioblast


high-resolution terminology - matching measurements at high-resolution


Adenine nucleotides

Description

Adenine nucleotides are a group of organic molecules including AMP, ADP and ATP. These molecules present the major players of energy storage and transfer. Their structures comprise the purine base adenine, a five-carbon sugar and one to three phosphate groups.(for further information see text below)

Abbreviation: AN


MitoPedia topics: Substrate and metabolite 


Adenine nucleotides and energy transfer

Adenine nucleotides, which are also generally called adenosines or adenylates by some people, have the typical structure of nucleotides but feature an additional adenine, which is attached to the ribose sugar moiety of the nucleotide. The three most popular members of this family are the purine nucleotides AMP, ADP and ATP, which can be converted into each other by the addition or removal of one to two phosphate groups. This process stores or releases energy and is thereby essential for energy transfer and supply of multiple cellular reactions. The breaking of one phosphoanhydride bond releases 7.3 kcal/mol of energy. With this the dephosphorylation of the energy-rich ATP to ADP yields a free energy of 30.5 kJ/mol or even 61 kJ/mol when two phosphate groups are released (as shown below). The reaction is carried out by the enzyme adenylate kinase (ADK or myokinase).

  • ATP + H2O β†’ ADP + Pi : : : : : Ξ”G = -30.5 kJ/mol
  • ADP + H2O β†’ AMP + Pi : : : : : Ξ”G = -30.5 kJ/mol
  • ATP + H2O β†’ AMP + 2Pi  : : : : Ξ”G = -61 kJ/mol

To restore the energy, an endergonic reaction, in which ATP is created from ADP and a free phosphate is needed. This reaction can be carried out by the membrane embedded ATP synthase (also called complex V). The energy which is used to generate ATP from ADP and Pi is hereby available in the form of hydrogen ions (H+), which are moved down an electrochemical gradient, e.g. from the intermembrane space into the mitochondrial matrix.

ATP and the free energy, which can be stored or generated by its conversion into ADP and AMP, is useful in many cellular processes, especially cellular respiration. It serves as an energy source for glycolysis, photosynthesis, beta oxidation, anaerobic respiration, active transport mechanisms across the cell membrane -e.g. in the electron transfer system-, and synthesis of macromolecules such as DNA.

Nucleotides

Nucleotides are organic molecules and are made up of three subunits: a nitrogenous base (purine or pyrimidine base), a five-carbon sugar (ribose or deoxyribose) and one to three phosphate groups. With this, in short, nucleotides are nucleosides with attached phosphate group(s). Nucleotides present the building blocks of nucleic acids and by this form essential biomolecules of life like for example deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). In addition, they make up components that play important roles in biochemical processes, namely nucleoside triphosphates (ATP, GTP, CTP and UTP), which can store and transfer energy (by the conversion of ATP to ADP), or cAMP and cGMP, which participate in cell signalling (cGMP and cAMP). Some nucleotides are also incorporated into important cofactors of enzymatic reactions, for example coenzyme A, FAD, FMN, NAD, and NADP+, and therefore serve essential cellular functions.