Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 28 : DNA and RNA Structures and Protein Synthesis

5 steps in protein synthesis

1. DNA serves as a code for proteins
2. Transcription occurs. One strand of DNA serves as a template (blueprint) for the formation of mRNA.
3. after transcription, the newly formed mRNA goes into the cytoplasm and attaches to a ribosomes.
4. tRNA which carry specific amino acids, have anticodons which bind complementarily with the mRNA triplet codons
5. The ribosome moves along the mRNA strand reading each codon (a triplet having 3 bases). The tRNA anticodon binds to it’s complementary codon. The amino acid carried by the tRNA is bonded to the polypeptide. The ribosome moves down the mRNA strand one codon at a time releasing a tRNA as it does and making room for another tRNA carrying an amino acid to join the mRNA.

1. DNA - carries the blueprint for the order of amino acids to be produced during protein synthesis.
2. Messenger RNA (mRNA) - copies the DNA molecule in the nucleus during transcription and goes into the cytoplasm and attaches itself to a ribosome. One 3 letter unit in an mRNA chain is called a codon.
3. Transfer RNA (tRNA) - drops off amino acids it is coded to carry at the ribosome. The 3 letter code is complementary to mRNA and this 3 letter code is called the anti-codon
4. Ribosome (rRNA) - this is where protein synthesis occurs. (Where the protein is assembled)