Can explain the process of polypeptide synthesis in the cell?

Protein synthesis is known as the central dogma of biology, it is the reason our cells and hence our bodies can function. It is the conversion of DNA bases (A,T,G,C) intro an intermediary form called RNA (U,T,G,C) to then code for the joining and formation of an initial primary polypeptide structure. The initial stage of protein synthesis is called transcription helicase breaks the H-bonds of DNA and exposes a single template strand for RNA polymerase to bind to a designated promoter site to create a pre-mRNA strand (this involves complementary base pairing). As the DNA closes up in eukaryotes, a terminal codon (set of three bases) notifies RNA polymerase to stop transcribing and to detach; the pre-mRNA is spliced to remove unnecessary introns and join together the exons within the nucleus. mRNA now leaves the nucleus via a nuclear pore.Translation occurs in the nucleus and is where the information (base arrangement) stored in mRNA codes for a specific polypeptide chain. The mRNA is read inside a ribosome where two corresponding tRNA proteins enter and bring two amino acids at a time. The tRNA is a clover-leave shaped ribosome that is formed by having an anticodon and a separate amino acid end. The anticodon is specific to the three base codon of the mRNA and has a corresponding amino acid to the codon attached at its distal end. When two tRNA proteins enter the ribosome, they bind to their mRNA counterparts and the amino acids join via a condensation reaction to form a covalent peptide bond. This process occurs in opposite directions, such that mRNA enters the ribosome in one direction and the amino acid bound tRNA enters, binds and leaves in the opposite direction. This continues until a full primary structure polypeptide chain forms in the opposite direction to mRNA translation and in the same direction as the tRNA. Stopping occurs when a stop codon is read in the translation of mRNA. The primary structured polypeptide can further fold and join other polypeptides to create tertiary and quaternary structures, hence becoming a fully functioning protein.

Answered by Zak M. Biology tutor

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