Protein Synthesis How a cell uses the DNA code to build proteins! Protein Synthesis: Basics • Amino acids are the building blocks of proteins • Amino acids are determined by the sequence of nucleotides Protein Synthesis: Basics • What you need to build proteins: –Instructions (DNA) –Parts (amino acids) –Workers (RNA) Protein Synthesis: Basics • 3 types of RNA: 1.mRNA = messenger • DNA message from nucleus to ribosome 2.tRNA = transfer • Transports amino acids to ribosome 3.rRNA = ribosomal Protein Synthesis: Basics DNA • Deoxyribose sugar • Double sided • A, T, C, G RNA • Ribose sugar • Single sided • A, U, C, G In RNA: Uracil, not Thymine, pairs w/ Adenine! Protein Synthesis: Transcription • From DNA to mRNA • Occurs in the nucleus • Enzymes make a RNA copy of a segment of DNA –Just like DNA replication except A pairs with U, not with T Protein Synthesis: Transcription 1. DNA = TACGCATGA mRNA = AUGCGUACU 2. DNA = TACACGATT mRNA = AU G U G C UAA Protein Synthesis: Translation • From mRNA to protein • Occurs at a ribosome Protein Synthesis: Translation • There is a total of 20 amino acids, but there are only 4 nitrogen bases… • So, how many bases must be grouped together for at least 20 possible combinations? –1 base = 41 = 4 –2 bases = 42 = 16 –3 bases = 43 = 64 Protein Synthesis: Translation • Three nucleotides of mRNA code for one amino acid • Codon = 3 nucleotides of mRNA • For example: AAA codes for lysine –AAA is the mRNA codon –Lysine is the amino acid Protein Synthesis: Translation • Use the table on p. 292 to identify the correct amino acid from the following mRNA codons: mRNA 1. UCC 2. GCG 3. GGA 4. CUU Amino acid 1. Serine 2. Alanine 3. Glycine 4. Leucine Protein Synthesis: Translation • Key codons: –AUG = start (methionine) –UAA, UGA, & UAG = stop Protein Synthesis: Translation • tRNA brings aa’s to the ribosome • Each tRNA attaches to only one type of amino acid, but how does it know which one is needed? • Each tRNA has a sequence of 3 nucleotides (anticodon) • tRNA anticodon pairs w/ the mRNA codon Protein Synthesis: Translation • Identify the tRNA anticodon: codon 1. ACU 2. UGC 3. GUA 4. UGU anticodon 1. UGA 2. ACG 3. CAU 4. ACA Protein Synthesis: Translation • tRNA structure: Protein Synthesis: Translation Protein Synthesis: Translation 1. Start codon (AUG) attaches to ribosome 2. tRNA anticodon (UAC) pairs w/ mRNA codon transporting Met- to the ribosome Protein Synthesis: Translation 3. Ribosome slides along mRNA to next codon • This process continues until STOP codon Protein Synthesis: Translation • Amino acids joined by peptide bonds • This long string of amino acids is now a protein! Protein Synthesis: Recap Protein Synthesis: Recap 1. DNA = TACCCCATT mRNA = AU G G G G UAA codons = (AUG) (GGG) (UAA) aa’s = Met - Gly - Stop anticodon = (UAC) (CCC) (AUU) Protein Synthesis: Recap 2. DNA = TACGTGACT mRNA = AUGCACUGA codons = (AUG) (CAC) (UGA) aa’s = Met - His - Stop anticodon = (UAC) (GUG) (ACU) Translation Game: How to Play Goal = build a protein by connecting the proper sequence of amino acids! 1. Transcribe the DNA strand to mRNA 2. Use p. 292 to translate the mRNA into a chain of amino acids Translation Game: How to Play • Only one person out of seat per team • You are finished when every member of your team is seated with a hand raised Translation Game: Scoring 1st Place = 6 pts 2nd Place = 5 pts 3rd Place = 4 pts 4th Place = 3 pts 5th Place = 2 pts 6th Place = 1 pt *0 pts if your team doesn’t finish.