2. Peptide Bond Formation

3. Walk the Dogma RECALL: The 4 types of organic molecules… CARBOHYDRATES LIPIDS PROTEINS (amino acid chains) NUCLEIC ACIDS (DNA and RNA) The CENTRAL DOGMA of CELL BIOLOGY

4. Remember: DNA contains the instructions that tells the cell how to make proteins Protein Synthesis has 2 main phases: Transcription (DNA → RNA) Translation (RNA → Protein)

5. DNA vs. RNA DNA -Deoxyribose Sugar -Double-stranded - A binds to T RNA - Ribose Sugar - Single-stranded - A binds to U (Uracil)

6. Ribonucleic Acid (RNA) There are 3 types of RNA: Messenger RNA (mRNA) Structure: Linear Single Strand Function: Carries genetic info from the DNA in the nucleus to the cytoplasm Transfer RNA (tRNA) Structure: Hairpin Loop Function: Binds and carries specific amino acids Ribosomal RNA (rRNA) Structure: Globular Function: Combines with proteins to form ribosomes

7. Ribonucleic Acid (RNA)

8. Protein Synthesis: TRANSCRIPTION Transcription: the process by which genetic information is copied from DNA to RNA DNA double-strand “unzips” RNA polymerase (an enzyme) binds to a specific region on DNA called a promoter RNA polymerase travels along the gene, creating a chain of mRNA that is complementary to the strand of DNA RNA polymerase reaches the termination signal at the end of the gene & falls off the DNA strand

9. A specific segment on a strand of DNA, which encompasses the space between a promoter and a termination signal, that contains the instructions to make a single polypeptide DEFINITION: GENE

10. Post-Transcriptional Modification Occurs before translation can begin Introns are removed, exons are joined –Intron: Non-coding sections of a gene –Exon: Region of a gene that does code for protein This process a.k.a. mRNA SPLICING Catalyzed by a spliceosome (RNA/protein complex) Intron = “Intervening” Exon = “Expressed”

11. Translation’s Triplet Code REMEMBER : Through transcription, the cell has created a strand of mRNA The next step is to translate that sequence of (4) nucleotides (A, U, G, C) into a correlating sequence of (20) amino acids The genetic code of the mRNA is “read” by the ribosome 3 nucleotides at a time Each 3 consecutive nucleotides is called a CODON Each codon codes for a specific amino acid

12. Protein Synthesis: TRANSLATION mRNA leaves the nucleus and travels into the cytoplasm A ribosome finds and binds to mRNA’s START CODON A free-floating, amino-acid-carrying tRNA bearing the appropriate ANTICODON binds to the start codon The amino acid detaches from its tRNA The ribosome slides 3 nucleotides down the mRNA strand (THE PROCESS NOW REPEATS ITSELF) A free-floating, amino-acid-carrying tRNA bearing the appropriate anticodon delivers the next amino acid to the forming polypeptide The ribosome reaches the STOP CODON and falls off the mRNA, releasing the polypeptide (FINAL PRODUCT)