A-Level Biology AQA Notes

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Protein Synthesis

Transcription is the process of making messenger RNA from a DNA template.
DNA helicase breaks the hydrogen bonds between the DNA helix, free RNA nucleotides base pair with the exposed DNA template strand,
In prokaryotes, transcription results directly in the production of mRNA from DNA.
In eukaryotes, transcription results in the production of pre-mRNA; this is then spliced to form mRNA
Translation is the process of making proteins by forming a specific sequence of amino acids based on coded instructions in mRNA. RNA polymerase catalyses phosphodiester bonds between adjacent RNA nucleotides and the mRNA strand detaches, allowing the DNA helix to reform.
mRNA attaches to a ribosome on the rough endoplasmic reticulum, tRNA carries the corresponding amino acid to each codon on the mRNA one at a time, with an enzyme catalysing the formation of a peptide bond between amino acids using ATP, until a stop codon is reached and the peptide is released, folding into its tertiary structure.

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