Protein Synthesis

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Della Martina Woods
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1 Protein Synthesis

2 Objectives - To explain the central dogma - To understand the steps of transcription and translation in order to explain how our genes create proteins necessary for survival.

3 Review - What is DNA? - Where is it located? - What are proteins? - Where are they located?

4 Central Dogma

8 Types of RNA - mrna= Messenger RNA: takes the code from the DNA and brings it to the ribosome. It is made during first step called transcription. - rrna= Ribosomal RNA: combines with proteins to make the structure of the ribosome. - trna= Transfer RNA: carries an amino acid to the ribosome to be able to synthesize the protein during translation.

9 Overview of Protein Synthesis 3 Processes: - Transcription: we take the code from the DNA and turn it into messenger RNA to send to the ribosome. - RNA Processing: we modify the mrna to get rid of noncoding regions. (only in Eukaryotes!) - Translation: we use the code from the mrna to determine which amino acids will be brought over by the trna to construct our polypeptide chain.

10 Transcription - In transcription we transcribe a strand of mrna from a gene. - What is a gene? - How many genes are on a chromosome? - What makes genes different from each other? - How do we know what to transcribe?

11 Steps of Transcription 1. Initiation 2. Elongation 3. Termination *similar to replication although less enzymes are required

12 Lets watch... com/sites/ /student_view0/chapter3/animation mrna_ synthesis transcription quiz_1_.html

13 1. Initiation - RNA Polymerase attaches to the template strand of DNA at the promoter region. (RNA Polymerase does it all!) - The promoter is a specific sequence that marks the beginning of a gene.

14 2. Elongation - RNA Polymerase begins adding RNA nucleotides that are complementary to the template strand in the 3 direction.

15 3. Termination - RNA polymerase continues until it gets to the termination sequence. - Termination sequence is a special sequence that signals the end of the gene.

16 Grab your paper plasmid! Transcribe the insulin gene into MRNA and write it on the back of the plasmid.

17 Do Now - Use your phones to complete the socrative quiz! - Go to socrative.com and click student login - Enter classroom # and enter your name. - Answer the questions to the best of your ability without using your notes. - This will NOT be graded

18 Continuing Protein Synthesis 1. Transcription 2. mrna Processing 3. Translation

19 mrna Processing - Eukaryotic mrna is processed before leaving the nucleus. - This does NOT happen in prokaryotes.

20 mrna Processing Additions: - 5 cap is added (a single G nucleotide) - A poly A tail is added to the 3 end ( adenine nucleotides) * These are both added for protection against cellular enzymes and also facilitate ribosomal binding. * They are NOT translated as part of the protein.

21 Coding and Non-coding sequences - Most genes have both coding sequences called exons and non-coding sequences called introns. - Before the mrna leaves the nucleus the introns are removed. - Exons are then spliced together. They can splice in different ways to produce different proteins.

22 Practice With Transcription and Processing - Complete the mrna Processing practice worksheet with a partner. - We will go over it once you are done!

23 What labs have we done in our Biotech unit? Give your own summary of each lab and be prepared to discuss DNA Extraction 2. Restriction Digest 3. Paper Plasmid 4. DNA Goes to the Races

24 PCR- Polymerase Chain Reaction - Complete the PCR activity!

25 Do Now - Use your phones to complete the socrative quiz! - Go to socrative.com and click student login - Enter classroom # and enter your name. - Answer the questions to the best of your ability without using your notes. - This will NOT be graded *Also, hand in your outlines!

26 Continuing Protein Synthesis 1. Transcription 2. mrna Processing 3. Translation

27 Translation - Process occurring at the ribosome (in cytoplasm) - The RNA-->Protein portion of the central dogma - Involves ALL THREE types of RNA (NO DNA!!) - mrna codes for the amino acids of the protein which are brought over by trna and the protein is assembled by the ribosome.

28 Proteins - What do we already know about proteins? - What are they made up of? - What types of bonds hold them together? - How do the bonds form?

29 Steps to Translation 1. Initiation: - The 5 end of the mrna feeds through the ribosomes until it stops at the start codon- AUG. - A codon is 3 bases on the mrna that code for a specific amino acid. - - The first trna anticodon will hydrogen bond with AUG in the P site and deliver the first amino acid, Methionine. - An anticodon is 3 bases on the trna

30 Codons - A codon will code for a specific amino acid. - Each amino acid can have from 1-6 codons that will code for them. - Ex: Leucine has 6 different codons whereas methionine only has 1!

31 Ribosome Structure - The ribosome has 2 subunits - 1 large - 1 small - The mrna feeds through the subunits to make the protein.

Ribosomal Grooves - Also called sites - (APE) - A Site:initial binding site for the trna carrying new amino acids (*First trna binds to P, all others bind to A) - P

32 Ribosomal Grooves - Also called sites - (APE) - A Site:initial binding site for the trna carrying new amino acids (*First trna binds to P, all others bind to A) - P Site:contains the growing polypeptide chain as the amino acids link and form peptide bonds. - E Site: (not shown in all models) site where the trna exits once it has delivered its amino acid.

33 Codon Charts

34 Codon Chart Practice Identify the amino acids coded for by the following codons: - UUU - ACG - CAC - UAA*

35 Steps to Translation 2. Codon Recognition: - The next trna anticodon will hydrogen bind to the mrna codon in the A site.

36 Steps to Translation 3. Bond Formation: The amino acid in the P site will form a peptide bond with the amino acid in the A site.

37 Steps of Translation 4. Translocation: - The trna and mrna shift and the trna separates from the mrna and is released from the E site.

38 Steps of Translation 5. Repeat: - This process repeats numerous times depending on how long the mrna is.

39 Steps to Translation 6. Termination: - trnas keep delivering amino acids until it reaches a stop codon on the mrna. - Use your chart to determine the 3 stop codons.

40 Steps to Translation com/sites/ /student_view0/chapter3/animation how_t ranslation_works.html

41 Practice - Take out the transcription/processing worksheet from yesterday and translate all of the sequences using your codon chart!

DNA codes for RNA, which guides protein synthesis.

Section 3: DNA codes for RNA, which guides protein synthesis. K What I Know W What I Want to Find Out L What I Learned Vocabulary Review synthesis New RNA messenger RNA ribosomal RNA transfer RNA transcription