Hvor kommer energien til dna syntese fra?
DNA replication
DNA-polymerase tilføjer en ny DNA-streng ved at forlænge 3'-enden af en eksisterende nukleotidkæde og tilføje nye nukleotider til skabelonstrengen en ad gangen via dannelsen af phosphodiesterbindinger. Energien til denne DNA-polymerisationsproces kommer fra hydrolyse af de højenergiske fosfatbindinger (fosforanhydrid) mellem de tre fosfater, der er knyttet til hver enkelt ikke-indkorporeret base. Frie baser med deres tilknyttede fosfatgrupper kaldes nukleotider; især baser med tre tilknyttede fosfatgrupper kaldes nukleosidtriphosphater. Når et nukleotid tilføjes til en voksende DNA-streng, ledsages dannelsen af en fosfodiesterbinding mellem nukleotidets proximale fosfat og den voksende kæde af hydrolyse af en højenergifosfatbinding med frigivelse af de to distale fosfater som pyrofosfat. Enzymatisk hydrolyse af det resulterende pyrofosfat til uorganisk fosfat forbruger en anden fosfatbinding med høj energi og gør reaktionen reelt irreversibel[Note 1].
DNA replication
DNA polymerase adds a new strand of DNA by extending the 3' end of an existing nucleotide chain, adding new nucleotides matched to the template strand one at a time via the creation of phosphodiester bonds. The energy for this process of DNA polymerization comes from hydrolysis of the high-energy phosphate (phosphoanhydride) bonds between the three phosphates attached to each unincorporated base. Free bases with their attached phosphate groups are called nucleotides; in particular, bases with three attached phosphate groups are called nucleoside triphosphates. When a nucleotide is being added to a growing DNA strand, the formation of a phosphodiester bond between the proximal phosphate of the nucleotide to the growing chain is accompanied by hydrolysis of a high-energy phosphate bond with release of the two distal phosphates as a pyrophosphate. Enzymatic hydrolysis of the resulting pyrophosphate into inorganic phosphate consumes a second high-energy phosphate bond and renders the reaction effectively irreversible.[Note 1]
DNA replication