PROTEIN SYNTHESIS. copyright cmassengale

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1 PROTEIN SYNTHESIS 1

2 DNA and Genes 2

3 Roles of RNA and DNA DNA is the MASTER PLAN RNA is the BLUEPRINT of the Master Plan 3

4 RNA Differs from DNA RNA has a sugar ribose DNA has a sugar deoxyribose 4

5 Other Differences RNA contains the base uracil (U) DNA has thymine (T) RNA molecule is single-stranded DNA is doublestranded DNA 5

6 Structure of RNA 6

7 Central Dogma of Biology DNA codes for RNA which guides the synthesis of proteins! 7

8 . Three Types of RNA Messenger RNA (mrna) copies DNA s code & carries the genetic information to the ribosomes Ribosomal RNA (rrna), along with protein, makes up the ribosomes Transfer RNA (trna) transfers amino acids to the ribosomes where proteins are synthesized 8

9 amino acid attachment site mrna UA C anticodon trna rrna 9

10 Central Dogma of Biology Step 1 DNA codes for RNA which guides the synthesis of proteins! 10

11 TRANSCRIPTION IS HAPPENING AT THE SAME TIME AS DNA REPLICATION! 11

12 Transcription - 1 A portion of the DNA molecule unzips Recall: DNA helicase is the enzyme responsible for this! 12

13 Transcription - 2 RNA polymerase joins RNA nucleotides using the DNA strand as a template This strand of DNA read by the RNA is the template strand read in the 3 to 5 This new strand of RNA is the mrna strand made in the 5 to 3 direction 13

14 14

15 Transcription - 3 The mrna strand is released through nuclear pores (exits the nucleus) and the DNA strand rejoins 15

16 RNA Polymerase 16

17 mrna Processing After the DNA is transcribed into RNA, editing must be done to the nucleotide chain to make the RNA functional Introns, non-functional segments of DNA are snipped out of the chain 17

18 mrna Editing Exons, segments of DNA that code for proteins, are then rejoined by the enzyme ligase The newly processed mrna can then leave the nucleus 18

19 Result of Transcription CAP New Transcript Tail 19

20 mrna Transcript - 4 mrna leaves the nucleus through its pores and goes to the ribosomes 20

21 The Genetic Code A codon designates an amino acid An amino acid may have more than one codon There are 20 amino acids, but 64 possible codons Some codons tell the ribosome to stop translating 21

22 The Genetic Code Use the code by reading from the center to the outside Example: AUG codes for Methionine 22

23 Name the Amino Acids GGG? UCA? CAU? GCA? AAA? 23

24 Remember the Complementary Bases On DNA: A-T C-G On RNA: A-U C-G 24

25 Question: What would be the complementary RNA strand for the following DNA sequence? DNA 5 -GCGTATG-3 25

26 Answer: DNA 5 -GCGTATG-3 RNA 3 -CGCAUAC-5 26

27 Translation Translation is the process of decoding the mrna into a polypeptide chain to create proteins Ribosomes read mrna three bases or 1 codon at a time and construct the proteins 27

28 Transcription Translation 28

29 Ribosomes Composed of rrna (40%) and proteins (60%) Have two sites for trna attachment --- P and A 29

30 Step 1- Initiation mrna transcript start codon AUG attaches to the small ribosomal subunit Small subunit attaches to large ribosomal subunit mrna transcript 30

31 Ribosomes Large subunit P Site A Site Small subunit 31 mrna A U G C U A C U U C G

32 Step 2 - Elongation As ribosome moves, two trna with their amino acids move into site A and P of the ribosome Peptide bonds join the amino acids 32

33 Initiation aa1 aa2 anticodon hydrogen bonds 1-tRNA 2-tRNA U A C G A U A U G C U A C U U C G A codon mrna 33

34 Elongation peptide bond aa1 aa2 aa3 3-tRNA anticodon hydrogen bonds 1-tRNA 2-tRNA G A U A C G A U A U G C U A C U U C G codon mrna 34 A A

35 aa1 aa2 peptide bond aa3 1-tRNA U A C (leaves) 2-tRNA 3-tRNA G A A G A U A U G C U A C U U C G A Ribosomes move over one codon mrna 35

36 aa1 peptide bonds aa4 aa2 aa3 2-tRNA 3-tRNA G A U G A A A U G C U A C U U C G A 4-tRNA G C U A C U mrna 36

37 aa1 peptide bonds aa2 aa3 aa4 G 2-tRNA A U (leaves) 3-tRNA G A A A U G C U A C U U C G Ribosomes move over one codon A 4-tRNA G C mrna 37 U A C U

38 aa1 aa2 peptide bonds aa3 aa4 aa5 5-tRNA U G A 3-tRNA 4-tRNA G A A G C U G C U A C U U C G A A C U mrna 38

39 aa1 aa2 peptide bonds aa3 aa4 aa5 5-tRNA 3-tRNA G A A 4-tRNA G C G C U A C U U C G U A A C U Ribosomes move over one codon U G A mrna 39

40 aa4 aa5 aa199 Termination aa3 aa2 primary structure of a protein aa200 aa1 A C U C A U G U U mrna 200-tRNA terminator or stop codon U A G 40

41 End Product The Protein! aa2 The end products of protein synthesis is a primary structure of a protein A sequence of amino acid bonded together by peptide bonds aa3 aa4 aa5 aa199 aa1 aa200 41

42 Messenger RNA (mrna) mrna start codon A U G G G C U C C A U C G G C G C A U A A codon 1 codon 2 codon 3 codon 4 codon 5 codon 6 codon 7 protein methionine glycine serine isoleucine glycine alanine stop codon Primary structure of a protein aa1 aa2 aa3 aa4 aa5 aa6 peptide bonds 42