Protein Synthesis

DNA

DNA RNA Proteins (Transcription) (Translation)

• DNA (genetic information stored in genes)

• RNA (working copies of genes) • Proteins (functional molecules)

WHAT’S THE POINT?

• Protein Synthesis is the process whereby DNA encodes for the production of amino acids and proteins.

• Proteins are chains of amino acids bonded together.

• Protein synthesis takes place in two parts:

o Transcription – the formation of mRNAo Translation – the formation of amino

acid chains by reading the mRNA.

PROTEIN SYNTHESIS

• Transcription is the synthesis of messenger RNA (mRNA).

• Begins when RNA polymerase recognizes and binds to the promoter region on the double stranded DNA molecule.

• RNA polymerase moves along the template strand of the DNA, making the complementary single stranded messenger RNA molecule.

TRANSCRIPTION

• Synthesis is in the 5’ to 3’ direction, with new nucleotides being added to the 3’ end of the growing mRNA molecule. (Copying the 3’ to 5’ side of DNA)

• As the RNA polymerase advances along, it breaks the hydrogen bonds in front, and allows the previous broken bonds to reform, closing the gap in the DNA strand.

TRANSCRIPTION

• When RNA polymerase reaches a specific sequence of nucleotides on the DNA called transcription terminator, the RNA polymerase and mRNA stop coding and dissociate from the DNA.

• The newly formed mRNA must then travel from inside the nucleus to a ribosome (rRNA) located outside the nucleus to be translated.

• Lets take a look: http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__mrna_synthesis__transcription___quiz_1_.html

TRANSCRIPTION

TRANSCRIPTION

• Translation begins when mRNA binds to the ribosome (rRNA). The initial transfer RNA (tRNA) occupies the P site on the ribosome. Subsequent tRNAs, with attached amino acids, first enter the ribosome at the A site.

• Codon – group of three nucleotides on mRNA

• Anticodon – complementary group of three nucleotides on tRNA

TRANSLATION

• The mRNA passes along the ribosome, three nucleotides at a time.

• As the mRNA is read by the ribosome, the tRNAs move from the A site, to the P site, and finally to the E site. Their amino acids are connected to form a chain and the used tRNA in the E site is released.

• Each time a new Codon sequence moves into the A site, a new tRNA brings an amino acid.

TRANSLATION

• Eventually, the ribosome encounters a stop codon on the mRNA. The ribosomal complex falls apart and the protein (amino acid chain) is released into the cell.

• Lets take a look: http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__

how_translation_works.html • tRNA Anticodons = Amino Acids =

Proteins

TRANSLATION

TRANSLATION

• Amino acids are the building blocks of proteins.

• 20 different amino acids are used to synthesize our body’s proteins.

• tRNA Anticodon AUG = Start = Methionine

• tRNA Anticodons UAA, UAG, & UGA = Stop and has No Amino Acids associated with these.

• Amino acids are joined by peptide bonds. When many amino acids are joined, it is called a polypeptide.

AMINO ACIDS

Alanine Ala Arginine Arg Asparagine Asn Aspartic acid Asp Cysteine Cys Glutamic acid Glu Glutamine Gln Glycine Gly Histidine His Isoleucine Ile

Leucine Leu Lysine Lys Methionine Met Phenylalanine Phe Proline Pro Serine Ser Threonine Thr Tryptophan Trp Tyrosine Tyr Valine Val

AMINO ACIDS