Protein Synthesis

1. Protein Synthesis Making Proteins

2. Why do we need protein synthesis? • Cell Structure • (80% of cell membrane is proteins) • Transport Channels • Cell Processing • Hormones (signals) • Enzymes • What else?

3. What do we need for Protein Synthesis? • DNA • Is the template for making mRNA during transcription • RNA • mRNA =messenger RNA • Makes and takes copy DNA to cytoplasm

4. tRNA = transfer RNA • Matches with mRNA on ribosomes • Carries Amino Acids • rRNA = ribosomal RNA • Part of ribosome • Reads mRNA • Directs tRNA • 3. Ribosome • Reads mRNA • Directs tRNA • Creates peptide bonds between AA’s

5. 4. Amino Acids (AA’s) • Building blocks of proteins • (20 AAs essential) • Protein = AA chain = polypeptide chain • ORDER MATTERS! • AA order determines f(x) of protein

6. Protein SynthesisOverview http://www.columbia.edu/cu/biology/courses/c2005/images/animtransln.gif

7. 2 main steps of Protein Synthesis TRANSCRIPTION: writing the message • DNAmRNA STEPS: • unwind DNA in nucleus with help of enzyme • DNA polymerase pairs RNA nucleotides with DNA nucleotides =mRNA • * U replaces T in RNA *

8. 3 DNA nucleotides (triplet) •  m RNA CODON Start Codon Codons

9. 2 main steps of Protein Synthesis TRANSLATION: • mRNA tRNA Protein (AA chain) Steps: • mRNA leaves nucleus and binds to ribosome • tRNA (anticodon) brings the amino acid to the mRNA (codon) on ribosomes

10. Ribosomes move down mRNA to next codon • tRNAanticodon brings and attaches next AA with peptide bond • tRNA leaves ribosome once AA attached • Repeat above steps to add AA until STOP CODON to signal end of protein • UAG, UAA, or UGA • Polypeptide chain releases from ribosomes

11. A U G G G C U U A A A G C A G U G C A C G U U • This is a molecule of messenger RNA. • It was made in the nucleus by transcription from a DNA molecule. codon mRNA molecule

12. ribosome A U G G G C U U A A A G C A G U G C A C G U U A ribosome on the rough endoplasmic reticulum attaches to the mRNA molecule.

13. Amino acid tRNA molecule anticodon U A C A U G G G C U U A A A G C A G U G C A C G U U A transfer RNA molecule arrives. It brings an amino acid to the first three bases (codon) on the mRNA. The three unpaired bases (anticodon) on the tRNA link up with the codon.

14. U A C C C G A U G G G C U U A A A G C A G U G C A C G U U Another tRNA molecule comes into place, bringing a second amino acid. Its anticodon links up with the second codon on the mRNA.

15. Peptide bond C C G U A C A U G G G C U U A A A G C A G U G C A C G U U A peptide bond forms between the two amino acids.

16. C C G U A C A U G G G C U U A A A G C A G U G C A C G U U The first tRNA molecule releases its amino acid and moves off into the cytoplasm.

17. C C G A U G G G C U U A A A G C A G U G C A C G U U The ribosome moves along the mRNA to the next codon.

18. C C G A A U A U G G G C U U A A A G C A G U G C A C G U U Another tRNA molecule brings the next amino acid into place.

19. C C G C C G A U G G G C U U A A A G C A G U G C A C G U U A peptide bond joins the second and third amino acids to form a polypeptide chain.

20. G U C A C G A U G G G C U U A A A G C A G U G C A C G U U The process continues. The polypeptide chain gets longer. This continues until a termination (stop) codon is reached. The polypeptide is then complete.

21. Synthesis Practice • DNA : A=T and C=G • RNA: A=U and C=G *So, when transcribing DNA into RNA “T” is replaced with “U” • Example: • Original DNA: ATCG • Complementary DNA: TACG • Transcription example: • Original DNA: ATCG • Messenger RNA: UACG • (CODON)

22. Practice Continued • Translation Example: • Messenger RNA: UACG • (CODON) • Transfer RNA: AUGC • (ANTICODON) • tRNA brings the AA so they can bond to make protein

23. Synthesis Practice UAC AUG (start) GGA CCU GGA CCU UAU AUA UGA (stop) ACU

24. To determine the AA • Use mRNA codon and use the Universal Genetic Code Chart. • AUG (codon) • A = 1stbase • U = 2nd base • G = 3rd base