Protein Synthesis

DNA in the Cell

• The Central DogmaDNA RNA Protein

RNA

• Ribonucleic Acid• Like DNA it is composed of

nucleotides• Unlike DNA it is single

stranded, has a different sugar (Ribose), and contains Uracil instead of Thymine

• There are three main types of RNA involved in protein synthesis, messenger RNA, ribosomal RNA, and transfer RNA.

Step I: Transcription

• Occurs in the nucleus.

• Transcription is the process of converting the permanent instruction of DNA into the temporary instruction in mRNA.

Gene

• A gene is a segment of DNA that codes the instructions for one protein.

Transcription

• DNA Helicase unzips the DNA• RNA Polymerase adds complimentary

RNA nucleotides to the DNA of the gene.• DNA mRNA

Adenine = UracilCytosine = GuanineGuanine = CytosineThymine = Adenine

Step II: Translation

• mRNA travels to a ribosome where it is translated into proteins.

• The ribosome is composed of rRNA and associated proteins.

Translation

• A mRNA codon (three base sequence) enters a ribosome.

• At the ribosome, the mRNA codon bonds to the anticodon of a tRNA (Transfer RNA) that is transferring one amino acid.

The Genetic Code

• The mRNA continues moving through the ribosome, and as each new amino acids is brought it bonds to the previous amino acid creating a chain of amino acids (a Protein)

The Cytomembrane System

• The completed Protein may now travel in a Vesicle to the Golgi Body (where modified), and then in a Vesicle to the membrane or somewhere within the Cell