Protein Synthesis Help
Introduction Protein Synthesis
Within the cell nucleus are a number of chromosomes ( KROH -moh-sohms) or wormlike “colored” ( chrom ) “bodies.” Each of these chromosomes, in turn, contains a number of tightly coiled DNA molecules. There are numerous genes or sections strung along the DNA molecules.
A single gene provides a chemical code for the synthesis of a particular protein. As Figure 5.4 shows, part of the DNA double helix unwinds, exposing a group of DNA codons ( KOH -dahns). These codons consist of sets of three chemical bases.
During transcription, a copy of the exposed DNA bases is made. A messenger RNA (mRNA) molecule then results. The mRNA molecule moves out of the nucleus, and onto the surface of a ribosome. A series of individual transfer RNA (tRNA) molecules, each attached to a certain amino acid, also move towards the ribosomes.
The final major stage of protein synthesis is called translation. During this process, which occurs along the ribosomes, the nitrogen base language of the mRNA codons is translated or changed into the amino acid language of a certain protein.
The tRNA molecules match their bases up against complementary bases of the mRNA molecule. The amino acids attached at the other end of the tRNAs link together via peptide ( PEP -tide) bonds. The end result is a finished protein or polypeptide ( PAH -lee- pep -tide) – a combination of “many” (poly-) amino acids connected by peptide bonds in a coded order.
Each completed protein (polypeptide) detaches from a ribosome and begins to perform its special function within the cell.
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