ATP provides the energy needed to build RNA molecules during transcription.
Here's a breakdown of how ATP is used:
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ATP as a Precursor: ATP (adenosine triphosphate) is one of the four ribonucleoside triphosphates (along with GTP, CTP, and UTP) used as building blocks for RNA.
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Energy Source: When RNA polymerase adds a nucleotide to the growing RNA strand, it cleaves off two phosphate groups from the incoming nucleoside triphosphate (like ATP). This cleavage releases energy.
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Bond Formation: The energy released from breaking the high-energy phosphate bonds is used to create a phosphodiester bond between the incoming nucleotide and the 3' end of the existing RNA molecule. Essentially, the energy from ATP (or GTP, CTP, or UTP, depending on the nucleotide being added) is directly coupled to the formation of the RNA polymer.
In summary, ATP (and other nucleoside triphosphates) not only provides the building blocks for RNA but also fuels the transcription process by supplying the energy necessary for forming phosphodiester bonds between nucleotides.
